Thinking of a new car within the next year. I really like the new M5. But the 550 is also a good choice with the Areo kit.. So what do you think M5 or 550?

M5. There's just way too much weight to haul around in the 5 series.

Only approx 36 HP difference with the E39 M5 too the 550. What is the weight difference?

Both are good. I've driven a 545/6spd and it hauled ass. Never driven a E60M5. If you have the $'s I'd go M5. Either way I suspect you will be very happy.

I have driven the E60 M5 3 times and it is flippin unreal. Smooth as silk. great fit and finish in the interior. Not too mention the ridiculous amount of power. Better resale and one of my favorites......the F1 sound eminating from the exhaust at high RPM's

How would you compare the E39 M5 to the 550?

Apples and oranges? :stickoutt

M5, and you really are comparing 2 different cars. It's not always about the Aero Kit and the extra HP

How would you compare the E39 M5 to the 550?

I think the S62 will be more maintenance as the miles go up. The 4.8L in the 550 will be noticeably faster than your C350, but not quite like the E39M would be.

550 less maintenance issues, less power, newer

M5 speed, handling, styling

I'd say find a low mileage '03 E39 M5.

I thought you were talking about new cars. Just realized you were comparing the 550 to the E39 M5. Can't really compare the two, but if it were a choice. M5 still.

I am looking at a low mile 2003 M5. I even drove it. But the new 550 is starting to grow on me. The E39 M5 is half the price of a new one. Thanks for the info.

The 06 C350 blows my 90 535 out of the water in speed,but does not even come close as in driver feel. Its my wifes car but it's fun and easy to drive.

M5

I've never driven the M5. Those that have-doesn't it provide more of a hard-edged, performance feel than the 550? The 550 is quite insulated and cushy. Which for most potential buyers is a good thing.

Personally I would go M5 if you're going for drive feel. But if you want something only bec it's new but pretty fast go 550. But Im sticking with M5 as my answer.

neither. older m5s are nice but id rather take a newer 550i over an older m5. me personally tho, i would take a 2008 535i. theyre just as quick and maybe a hair faster than the 550i. gas nowadays is killer and a twin turbo 6 cylinder running just as fast as a v8 would be ideal imo. i dunno what bmw was thinking when they made the 535i just as fast as the 550i because i couldnt justify spending the extra like 20k for the 550i over the 535i. and dont give me the ooooo its a V8 crap because they all sound the same. bmw makes their v8s too quiet for anyone to notice its a v8 so theres really no point to it besides the status of it. but the 550i fully loaded is nearly as expensive as the new m5 not loaded up but the base m5 is basically a fully loaded 5 series with a v10. the new m5 with the v10 makes some noise tho, that would be worth paying money for. imo, the 550i is a worthless car lol.

2008 535i w/ m-aero package and optional wheels
http://img.photobucket.com/albums/v638/NewCents05/550i/1180560883.jpg
http://img.photobucket.com/albums/v638/NewCents05/550i/1180560890.jpg

i dunno about you but id take that over a 550i or old m5 anyday.

Really? the new 535 is just as fast as the 550? Hmm... i thought the 550 had 60 hp more than the 535? Plus doesn't the larger displacement in the 550 mean more low end torque?

Really? the new 535 is just as fast as the 550? Hmm... i thought the 550 had 60 hp more than the 535? Plus doesn't the larger displacement in the 550 mean more low end torque?

Check out the Proceed//Vishnu tuned 335's, all the same mods should work on a 535. Then you are talking about 400+hp to the wheels with matching or greater torque. That is E60 M5 territory. Even stock, it makes ~270 rwhp, which is more than an E39 540.

neither. older m5s are nice but id rather take a newer 550i over an older m5. me personally tho, i would take a 2008 535i. theyre just as quick and maybe a hair faster than the 550i. gas nowadays is killer and a twin turbo 6 cylinder running just as fast as a v8 would be ideal imo. i dunno what bmw was thinking when they made the 535i just as fast as the 550i because i couldnt justify spending the extra like 20k for the 550i over the 535i. and dont give me the ooooo its a V8 crap because they all sound the same. bmw makes their v8s too quiet for anyone to notice its a v8 so theres really no point to it besides the status of it. but the 550i fully loaded is nearly as expensive as the new m5 not loaded up but the base m5 is basically a fully loaded 5 series with a v10. the new m5 with the v10 makes some noise tho, that would be worth paying money for. imo, the 550i is a worthless car lol.

2008 535i w/ m-aero package and optional wheels
http://img.photobucket.com/albums/v638/NewCents05/550i/1180560883.jpg
http://img.photobucket.com/albums/v638/NewCents05/550i/1180560890.jpg

i dunno about you but id take that over a 550i or old m5 anyday.


The 550i is actually slightly quicker then 535i and at high rpms the 550i is much louder then a 535i.

I test drove both before settling for the 550i... the power delivery was much better in the 550i then a 535i.

yeah but like said about you drop a few k on a couple of mods and youre looking at near 400hp to the wheels. that will be untouchable by the 550 then.

yeah but like said about you drop a few k on a couple of mods and youre looking at near 400hp to the wheels. that will be untouchable by the 550 then.

No thanks... i don't need my warranty voided

Besides... no thanks on a first year twin turbo 3/5 series... the 335s are already visiting the service depts very often. Matter of fact i have a friend with a 335i coupe thats been sitting at the dealership for almost 2 months because the fuel pump is on back order.

neither. older m5s are nice but id rather take a newer 550i over an older m5. me personally tho, i would take a 2008 535i. theyre just as quick and maybe a hair faster than the 550i. gas nowadays is killer and a twin turbo 6 cylinder running just as fast as a v8 would be ideal imo. i dunno what bmw was thinking when they made the 535i just as fast as the 550i because i couldnt justify spending the extra like 20k for the 550i over the 535i. and dont give me the ooooo its a V8 crap because they all sound the same. bmw makes their v8s too quiet for anyone to notice its a v8 so theres really no point to it besides the status of it. but the 550i fully loaded is nearly as expensive as the new m5 not loaded up but the base m5 is basically a fully loaded 5 series with a v10. the new m5 with the v10 makes some noise tho, that would be worth paying money for. imo, the 550i is a worthless car lol.

2008 535i w/ m-aero package and optional wheels

i dunno about you but id take that over a 550i or old m5 anyday.
You can't get the 535i with the M-tech aero kit right now. The picture you posted is in fact a 2008 550i with M-tech aero kit and standard 172 wheels. Obviously, you have no idea how fast the 550i is. There is ZERO chance of a STOCK 535i being faster than a stock 550i.

You can't get the 535i with the M-tech aero kit right now. The picture you posted is in fact a 2008 550i with M-tech aero kit and standard 172 wheels. Obviously, you have no idea how fast the 550i is. There is ZERO chance of a STOCK 535i being faster than a stock 550i.

the 535i is slightly faster in the 0-60 and quarter mile STOCK than the 550i

M5 for me.

the 535i is slightly faster in the 0-60 and quarter mile STOCK than the 550i
Show the proof. Yeah, BMW is really going to shoot itself in the foot making the 535i faster than the 550i.

the 535i is slightly faster in the 0-60 and quarter mile STOCK than the 550i

Its actually the other way around...

I test drove both cars and the 535i didn't feel as fast... felt very sluggish in low rpms.

Feel wise the 535i felt about 1 second slower in 1/4 mile then the 550i

Only approx 36 HP difference with the E39 M5 too the 550. What is the weight difference?

Curb weight:

E39 M5: 4024 lbs
E60 550i: 3803 lbs

There's some confusion with unladen weight and curb weight (since BMW quotes unladen most of the time). However, it's roughly a 200 lb difference between the two cars, give or take.

uh....M5 duh....

As an E39 owner, I love my car... but I say get the 550. I am no big fan of the exterior styling of the E60/E61, but they drive like pure sex and must have fewer little gremlins than the older chassis (M's included).

If you don't believe me, cruise over to the E39 forum and start reading how many people are fixing stupid things like: buttons, window regulators, whole cooling systems, fans, bushings, etc, etc...

The M sport package and a set of wheels with a proper lip fix all the styling woes on the new car, by the way.

Oh yeah, keep the 535's off your list of must-haves until they figure out how to get the oil temperature down about 50 degrees F. I see big $$ maintenance futures for those cars running as hot as they seem to. Remember, this is BMW's first modern turbo engine.

Well you have to look at it like this.

If you by the E39 M5 you are buying a M car which does put you in a exclusive club(not talking $$$ and the e60 M5 trumps it but it is still a exclusive club). Second you are buying what is considered the Best 4 door sedan that was ever build though that was a few years ago. You will have a hard time finding a Beast owner who will disagree with you. The E39 is a great car and is fully loaded so thats good. It is a manual which is a drivers car. The chassis is a bit old but still is very good and some will say that it communicates much better than a E60. PLUS the E39 Looks awesome and will always be a classic looking car and how can you talk bad about the 5.0 engine

Now it is time for the e60 argument. You are now comparing it to a new chassis, new techonology(which brings w/ its own issues) new Motor and a new level of HP compare to the 540's. The E60 does not look nearly as Mean as the e39 but it grew on me and must have since I own one now. When looking comparing the HP they are pretty close 360 vs. 390 so your not going to feel like you are comparing a 525 vs a 550. It has the sport automatic or 6/M. I have driven the 650 w/ sport automatic(my dads) and I think for an automatic, it rocks. I love my new e60 compared to my 540I 6/M and I am glad that I made the switch. It is larger and I am fully aware that when I drive the e60 that I am in a bigger car......... ok lets finish this post.

So here it is.... GO WITH YOUR GUT. Don't listen to us.... What car do you want to fire up every morning and DRIVE. Are you going to open your garage door and look at the (enter car here) and just smile. You get in that car, turn that key, fire the engine and realize that until you walk away form that car and hit that Rondel you will feel that your commute was worth every mile and you do not regret your choice...... I love cars and love to drive them. A car is the WORST purchase a person can buy but the emotions it invokes make you forget the $$$ and forget that you loose money every mile you add to the clock.

Good Luck and any decision will be a good one.

the E60 M5 is worlds apart from the E39 M5

if you have the loot do the E60 M5 no other choice is acceptable.
For top end tghe 550 is not bad, but the 535 as stated above is slightly QUICKER

if you have the loot go with the E60 M5. No other choice is acceptable.
Top spped the 550.. but the 535 is QUICKER

if you have the loot go with the E60 M5. No other choice is acceptable.
Top spped the 550.. but the 535 is QUICKER IN

if you have the loot go with the E60 M5. No other choice is acceptable.
Top spped the 550.. but the 535 is QUICKER IN THE

Get

Get the

What the heck?

From driving my E34's I would say the 535 is quicker than the 550 or even M5 in the quarter but that is about it... after that POWER comes into play.
get the new M5 if you can... its worth it.. its a daily driver (400 horses) and a power car (507)

What the heck?

post whore just trying to get his posts up :rolleyes

dude you have a noble!?!?!??!?! omfg you are god i bow down before you i love those cars. too bad theyre going out of business.

the 535i is slightly faster in the 0-60 and quarter mile STOCK than the 550i

you need:help

get the 550i 6-sp with sport kit.

you need:help

http://www.edmunds.com/insideline/do/Drives/FullTests/articleId=121047

This Is a BMW, So Let's Start With Power
What does BMW's new twin-turbo 3.0-liter inline-6 engine do for the 5 Series? This 2008 BMW 535i test car with an automatic transmission effectively equaled the acceleration of a 2006 BMW 550i (http://www.edmunds.com/used/2006/bmw/5series/100645497/prices.html) equipped with a manual transmission. The 535i's 5.5-second acceleration to 60 mph proves a sedan doesn't need the 550i's V8 engine to be quick

the 535i is 250lbs lighter and tests have proven that its not really rated at 300hp maybe 300hp to the wheels but its more like 340-350ish to the fly while the 550i is rated 360 to the fly. and i guess if you dont want to void your warranty then dont get the procede chip but after it is up and you want more speed a 1500 dollar chip will give you near 400hp. i just think the 535i is a more logical choice.

You must believe everything you read on the internet. Take what Edmunds says with a grain of salt. I have friends who own 2007 550i that have gotten 5.1 and 5.2. I know of people achieving 5.0 in their 2007 550i. Don't believe the hype that Edmund spews.

http://www.edmunds.com/insideline/do/Drives/FullTests/articleId=121047

This Is a BMW, So Let's Start With Power
What does BMW's new twin-turbo 3.0-liter inline-6 engine do for the 5 Series? This 2008 BMW 535i test car with an automatic transmission effectively equaled the acceleration of a 2006 BMW 550i (http://www.edmunds.com/used/2006/bmw/5series/100645497/prices.html) equipped with a manual transmission. The 535i's 5.5-second acceleration to 60 mph proves a sedan doesn't need the 550i's V8 engine to be quick

the 535i is 250lbs lighter and tests have proven that its not really rated at 300hp maybe 300hp to the wheels but its more like 340-350ish to the fly while the 550i is rated 360 to the fly. and i guess if you dont want to void your warranty then dont get the procede chip but after it is up and you want more speed a 1500 dollar chip will give you near 400hp. i just think the 535i is a more logical choice.

5.5 seconds,hah! proves that BMW under rates their cars... my friends M45 sport is rated 5.4 seconds to 62mph and i have a car lenght on him by 70mph all day long.

NY550i, there's no more need to reason with people that don't have a 550i. They'll take what a mag prints and run with it as gospel. Bilal and Amalan don't have a 550i so how would they really know? As for me, I have a 545i and have driven my friend's 550i. We have engaged in spirited driving on occasion and the 550i beats me but not by much. I know how fast both these v8s are.

well my car has the same engine yours does and its doing 0-60 in about 5.7 which is faster than what mags say it is but some mags are right on the dot. ive had a 550i and a 335i for loaners for a couple of days before and i enjoyed the 335i alot more than the 550i and imho i think the 335i sounded cooler. i havent driven a 535i before but i can tell you right now that a 335i will beat a 550i without a doubt in my mind but im not sure about the 535i i still think it would be even if its anything like the 335i.

working at a BMW dealership, I've driven both the 535 and 550 extensively. Personally, I fell in love with the 535i. The power delivery is phenominal. There is virtually no lag under 3500, and once the turbos spool it is an incredible ride. The 550 felt way too insulated. The Valvetronic V8 is just too smooth. you literally don't feel the accelleration so it just feels like you are barely accellerating when all of a sudden you are doing 130mph. Also, the engine is far too quiet, which is quite a shame since the sound of it is incredible. So numbers wise, the 550i is going to be marginally faster while the overall driving experience is going to be much more enjoyable in a 535. With a $1k software reflash, the 535 would be an absolutely rediculous car. I'd take the 535 over a 550 any day, price difference aside.

Note: both cars I've driven have been fully loaded, but the 535 was steptronic while the 550 was a manual.

The 550 has the option of active steering and active roll. With those two options that car with out handle the E39 M5. The power in each is pretty close to each other.

active steering is garbage

You're a retard. And that's why it is used on the Formula Cars.

The same active steering system in BMWs is the same system in Formula cars?

Wow and you call me retarded.

You drive a 96 maxima...have you ever driven a BMW with it? You feel completely disconnected with the road. Thanks, have a great night.

Yes I am calling you a retard. It's the same system with some minor differences to make it to production so retards like yourself can learn to usedit correctly. The civilian production cars steering ratio is 10:1 and formula is 18:1. In formula one cars the active steering is always there. In production cars the ratio gets less and less the faster you go. When you hit about 70 mph, the steering is returned to a normal vehicle steering ratio. Anymore questions?

No I have not driven a BMW with active steering, I have driven several hundred with active steering, active roll, and some without. This is due to me working for BMW. If you had the comprehension level of a kid with down syndrome you would realize how this technology helps the vehicles performance and safety. Your welcome, retard.

Well I opted out for that option. I drove the 335 coupe with and without. Feels so much better without. IMO.

Oh yeah, just because you have a 335 coupe doesn't mean a damn thing. Just because I drive a 96 maxima doesnt mean a damn thing either. As you have just learned, don't judge what people know on what they drive. They will prove you a retard as I just did, more than once.

Though active steering is something useful if you get used to it its still not my style...

Which other production cars come with active steering besides BMW?

I don't understand why you attacked me when all I was saying was active steering is garbage. You still haven't proved to me why active steering is not that. All you told me were ratios that I am already familiar with. I know how the system operates. And by knowing how it operates and then going and test driving one with and then one without I can come to the conclusion that active steering is garbage. You act like you were the one that designed the system and I am directly offending you by saying that.

I have driven both and I say get the 550i. That thing is pimp...and it gets decent gas mileage too. The E39 M5 just feels O-L-D.

Both cars are great, and either would be worthy to own. I have spent a lot of time in the 550i (which I own) at the track, and have participated in the 2 day M school at the performance center. The M5 is very fast as one would expect, but it is also very heavy, and you feel the weight when on the track. I personally think the 550i out handles the M5 because of the weight difference. The M6 is far better than the 5. But, you will probably not be on a track, so what good is the power of the M5 if it cannot be enjoyed. My recommendation, for every day driving, and even an occasional HPDE event, you cannot go wrong with the 550i. (with or without active steering - I happen to have it and like it.)
vz

ps - If you want to enjoy all worlds, I bet the new 3 coupe is a blast - or an M3 - goes and handles.

3 coupe is great:)

The 335 is a nice ride, fast and comfortable. No noticeable turbo lag, feels like a V-8. For hard street or track use, an aftermarket transmission cooler is needed. I may buy one as a dedicated track vehicle after the new model bugs are removed.

The 550 is also fast and comfortable, a good daily driver. The M5 is significantly faster and requires more dedication to own. While some owners love their 6-sp trans, the SMG is the way to go if you value maximum performance.

I track my M5, needs wider R compound tires & wheels to handle the weight. Great car on the street, scalpel-like handling, great brakes & the power speaks for itself.

If you like the 3-series size, go with the 335. For the 5-series, the M5 is king, with honorable mention for the B5.

I own the 08 535 with the sport package and as much as i hate to say it the 535 is about .5 slower in the 1/4 mile. .. it is definetley not faster... however it is lighter and $12k cheaper... much better for everyday drivng with the 6 cylinder and has fat 18's with 235 tires in the back..looks exactley like the 07 550. But again.. not faster and the engine and exhaust are virtually silent...i still beat most cars because they don't know i have the turbo's.
M5 is king of the hill

Both cars are great, and either would be worthy to own. I have spent a lot of time in the 550i (which I own) at the track, and have participated in the 2 day M school at the performance center. The M5 is very fast as one would expect, but it is also very heavy, and you feel the weight when on the track. I personally think the 550i out handles the M5 because of the weight difference. The M6 is far better than the 5. But, you will probably not be on a track, so what good is the power of the M5 if it cannot be enjoyed. My recommendation, for every day driving, and even an occasional HPDE event, you cannot go wrong with the 550i. (with or without active steering - I happen to have it and like it.)
vz

ps - If you want to enjoy all worlds, I bet the new 3 coupe is a blast - or an M3 - goes and handles.

I don't think you can go wrong with any of the cars, all have pluses & minuses and are great in their own ways.

With that blanket endorsement, as I've had seat time with the 335, 550, M5 & M6, the following impressions (opinion):

335i Turbo - Great balance of power, balanced weight & size. Stiff chassis, good brakes and responsive steering. First turbo model I've driven that didn't feel like a forced-induction engine, throttle response is right now. With careful modification, 400+ h.p. should be attainable without sacrificing driveability or durability, the new M3 will have a contender.

A 550i-owning friend & I participated in a track event, then swapped vehicles and ran a segment together. I appreciated the smoother auto gear box, BMW handling and brakes. Driving my M5, he stayed on my tail, as I had stayed on his tail, when I was driving my M. Nothing wrong with the 550, it's a great car & probably easier to live with on the street, but the M's extra power, SMG, larger brakes, stiffer chassis, adjustable power & suspension and meatier tires give it the performance edge. Not a fair comparison.

If you want a 5-series with the M's power without sacrifice, the Alpina B5 is the best combination, probably why BMW doesn't import them as it does the B7. supercars dot net / cars / 3158 dot html.

Weight is the biggest downside with both big Ms. Track use is murder on OE tires, especially the fronts.

With a slight weight advantage, the M6 can be slightly faster than the M5. BMW is preparing a stripped down, light weight, M6 track version that will probably take the king of the hill crown. The subjective negatives I found when evaluating the M6 for purchase, were the 6-series small interior, $15k price difference and Bangle Butt.

go M5

I had a 550i Titanium Gray for over a year (2007) bought early 2006, just trade it in for an M5 new. Reason? power. The m5 is a different breed , is not a plain series 5, is an ANIMAL. Test drive it and you'll see what I am talking about. Once you push the M button on the steering wheel , you will never look back at the 550i

Well the e39 M5 is sold. So I am putting my money into a new shop. 36x40x14. Well take up looking for a new car when the shop is complete. Thanks for all the good thoughts.

Random thoughts on the subject.

1.) Mods - Steve Dinan sells chips, suspensions, exhaust systems, wheels and other parts for these models. As long as you stay with Dinan parts, your warranty coverage isn't affected. Any of his components that affect factory warranty are replaced by an equivalent Dinan warranty.

2.) Consider how you will be using your new BMW before buying. Will you be hauling a bunch of small kids or hauling around a track? Do you give smoothness or performance higher value? Driving in heavy city traffic or on the open road? Do you own your vehicles or lease?

Current M models require slightly more maintenance and are more expensive to own. The V-10 is designed to consume oil, one liter of Castrol 10W-60 ($6.95 to $9.95 per liter) every 500 to 3,500 miles. The harder it's driven the greater the consumption. I buy by the case to keep the price down. Gas mileage in city driving is between 8.5 & 14 mpg depending on how heavy your right foot is, the 18.5 gallon tank requires frequent fill ups. Michelin PS2s are the best tire, a set will cost ~$1,800 every 8,000 to 20,000 miles. You can go through a set in one weekend on the track, the only safe place to drive the car the way it was intended to be driven. There have been problems with the SMG, VANOS and other advanced electronics. Some drivers have complained their Ms spend more time in the shop than in their garage. Other drivers have had few problems. Complex cars with lots of advanced electronics.

On the other hand, very little you will meet on the street or track will be able to keep up. Yes, some 2-seat sports cars are marginally faster. The Ms drive like scalpels, allowing the car to cut through traffic like butter. They also attract attention. One guy followed me in traffic, cell phone held out the window, snapping pictures.

How much impulse control do you have? Ms require a degree of restraint, necessary to keep from running into trouble with either the laws of physics or law enforcement. My salesman told me about another customer who bought a M5, only to return a couple months later wanting to trade for a 550. He said the M's deceptive power scared him, he had close calls and wanted something slower and safer.

No matter what you buy, enjoy!!

Go straight to the BMW USA websight. Got to the 535i tecnical data then the 550i tecnical data and look at the 0-60 times. The 550i is DEFINININININININANTLTTLTLTLTL faster.

Are there admins on this forum. If there are than Bial needs to pict his favoriate Monopoly Peace(THE BOOT).!!!!!!!!!!!!!!!!!!!!!!!!!:eyecrazy:lol:ak:ro ck::rock::rock::rock::rock::rock::lightning:bj:spa nk:ban::ban::ban::ban::ban::ban::ky

I love the smileys on this forum.

I think they canceled the M6 CSL prodject.:confused

I don't think you can go wrong with any of the cars, all have pluses & minuses and are great in their own ways.

With that blanket endorsement, as I've had seat time with the 335, 550, M5 & M6, the following impressions (opinion):

335i Turbo - Great balance of power, balanced weight & size. Stiff chassis, good brakes and responsive steering. First turbo model I've driven that didn't feel like a forced-induction engine, throttle response is right now. With careful modification, 400+ h.p. should be attainable without sacrificing driveability or durability, the new M3 will have a contender.

A 550i-owning friend & I participated in a track event, then swapped vehicles and ran a segment together. I appreciated the smoother auto gear box, BMW handling and brakes. Driving my M5, he stayed on my tail, as I had stayed on his tail, when I was driving my M. Nothing wrong with the 550, it's a great car & probably easier to live with on the street, but the M's extra power, SMG, larger brakes, stiffer chassis, adjustable power & suspension and meatier tires give it the performance edge. Not a fair comparison.

If you want a 5-series with the M's power without sacrifice, the Alpina B5 is the best combination, probably why BMW doesn't import them as it does the B7. supercars dot net / cars / 3158 dot html.

Weight is the biggest downside with both big Ms. Track use is murder on OE tires, especially the fronts.

With a slight weight advantage, the M6 can be slightly faster than the M5. BMW is preparing a stripped down, light weight, M6 track version that will probably take the king of the hill crown. The subjective negatives I found when evaluating the M6 for purchase, were the 6-series small interior, $15k price difference and Bangle Butt.

I think they canceled the M6 CSL prodject.

Can you provide more info or a link? I ran a quick Google search and found nothing about a cancellation.

Concerning 535 vs 550, I'd probably go with the larger engine. All of BMW's models have become heavy weights and it's hard to beat more cubic inches to increase power. With any model, increase the power plant's breathing (larger throttle bodies and header exhaust system) and add Dinan software and you'll be making some serious h.p.

My M5 is currently in the shop getting the Dinan Stage 2 suspension and software. No top speed limiter and new 8,500 rpm redline. Plus-2 R-compound tires & wheels next. Play time at the track.