okay, this last question limits me to your answer. it all depends on what type of (sound system) setup you want to do. if you want to go all out with aftermarket components like (speakers, subwoofers, amplifiers, head units) then i would recommend nothing but Alpine Products. but, if you want to save money and just get your six disc changer to work in your e30 check out ebay.com and type in e36 radio. i just checked out the website to see how many are avaliable and i got about 15 results! which is good. this is one of the links on ebay with a bmw e36 radio that is compatible with your six disc changer -->
http://cgi.ebay.com/ebaymotors/BMW-E...WDVWQQtcZphoto. this is just one of many units on ebay.com. right now i dont have enough time to show you more results but i will post you more products as soon as i get off of work. also, go to Alpine USA Distributor website. they have several head units that you can check out. BUT MAKE SURE IT IS SIX DISC COMPATABLE <-- VERY IMPORTANT!! okay ill hit you back later.