Hi Im new here but Ive been observing without an account as soon as I found out I was getting a BMW E46 323i 00' on April 15 (about 4 months ago) and Ive done numerous searches on this forum about the topic but none are very clear as to what EXACTLY I need in order to keep the Head Unit for my E46 and just change the sub, and speakers and such. I have some basic electronic knowledge, but not when it comes to car audio by far. Anyways, I want to spend about $500 and I dont mind buying used to fit that budget. I want my car to thump with good bass but at the same time clear lyrics (I listen primarily to rap music AKA Jeezy, Jay-Z Nas, etc.) Any clear help is appreciated. Thanx

first off, breathe :) second, find the period key :)
to change the speakers, all you need to do is just that. nothing special, just swap em out.
adding the amp is where it gets a little tricky. your car already has an amp running the speakers and on top of that, it's a balanced signal getting sent everywhere (short explanation: 3 wires instead of two). So, from what i understand (I have aftermarket everything in mine, so i went a different route) you need a converter especially for the balanced signal that will convert that to RCA style connectors. Once you have that, it's just like any other install. Even easier, what with the battery in the trunk.
As far as amps and subs go... Well, you're going to get all kinds of answers for that. Everyone will say that this brand is better than that and yadda yadda yadda. In the end it comes down to what you think is best bang for the buck. In the end, for the price range you're looking at, most the things people will suggest will sound almost exactly the same. Especially since you'll be looking at a ported box since you mostly listen to rap. (ported is louder, boomier, but a bit more sloppy. perfect for rap/r&b/that type of thing).
Now, MY suggestion. For budget systems, I usually stick with crossfire subs and power acoustik amps. power acoustik is kind of a mid-name brand but with the heart of a big brand and crossfire is very well known, but i don't see their subs run too much anymore. if you want to buy one of either, the amp or sub, i can offer you a pretty good deal ;)
anyways, sorry for the long windedness. boring sunday night. hope that helped a little

Yeah it did, definitely. So what exactly do you have for sale? And what is your asking price? And how much does a converter cost and where do I buy it from? thanx

Sent you an email on that stuff. As far as cost and location for the converter, check BSW, one of the forum sponsors. seems to be a pretty big price range for that type of thing, but nothing costing too much.