Dude, don't want to sound like a hater but, $5K is a lot of $ to spend on all this stuff. Most people get by by spending less than 1/5 that amount and end up with a kick-*** complete carputer system. As far as audio is concerned, you could spend the rest of it on buying mb quart components and getting thigs custom fabbed for your dash but, again, is it worth it?
Anyways, read up on this board for tons of ideas (esp. those who have done systems with E46's) and good luck.