I would like to put a new system in my 840 the old one just wont cut it anymore. plus i havnt owned a cassette in years lol. I would like to put in new speakers, headunit, and a sub and amp setup.

1.when replacing the headunit do i have to have it professionally installed or can i find a wireing harness and do it myself?
2. do i need to replace all the wireing when installing new speakers and replacing the oem amp.
3.what is the best speaker sizes to change to?

You can do it all, You can get a HU adapter on ebay or most audio corner shops, It's easy because all the wiring is in the trunk alone with the batteries, That's a bonus! I only upgraded the wires on my Subs and rear deck, You can put up to 6.5's in your kick panels, I changed to components front and rear, 3.5" mids in the door panel where the original mid were, The Tweeters in the panels were replaced with the componet tweeters, 2 Mid Bass in the kicks and 2 tweets in the door panel, The other set were made to fit in the rear deck, All crossovers in the trunk with amps, You can see nothing has been changed but the head unit, Unless you open the Trunk! There you'll see the subs and capacitor, I'd say go for it, Worth every penny, The car holds audio sound good.

Man - LOTS in the archives on this one - you'll get your most complete answer by doing a quick search. However:
1) The HU swap is a piece of cake - typical BMW harness just about every car built during the 90s-but...
2) The system is configured so that the amp(s) receive a speaker level signal instead of a low-level signal. In other words, while the HU can be a plug and play swap, the amp is not. If you're going to replace the amp then you'll need to run a set of RCA jacks from the front to the amp. (Not major deal-just something you'll need to take it into account)
3) As far as replacing the speaker wire, you'll get some different opinions on this one. My vote is that as long as you're in there, you might as well do it right from the beginning. Couple that with the fact that if you use the stock stuff, you'll need to cut all the connectors from the ends of the wiring to use it - I'm not big on cutting anything on the wiring harness..
4) Changing speakers means working out a way to mount them as nothing fits in the stock locations with modifications. (Hint:search-you'll find that folks have tried many different approaches to this)

Good Luck!

...also no need to run Rca's from the front when using a HU with a monitor, All the rca plugs are in the brain, Which has a place in the trunk as well.

Thanks alot guys thats what i needed to hear. The jackass at the audio store was making sound like it was really complex and needed professionall installation... But he was just trying to make some money off me, just as i suspected .

Thanks alot guys thats what i needed to hear. The jackass at the audio store was making sound like it was really complex and needed professionall installation... But he was just trying to make some money off me, just as i suspected .

Yeah, you'll get that a lot with these cars. :rolleyes

hang in there ;)

Yeah, you'll get that a lot with these cars. :rolleyes

hang in there ;)

I'm sure he just didn't know any better :stickoutt