You can build an excellent car system without "8 amps" - it all depends how much you want to spend. For a very reasonable amount you can pick up focal utopia components, ppi amps, a good sq (sound quality) sub, the best bargain being an infinity perfect 12.1. For the head unit, try nakamichi - the 45z has the best quality out there, and looks absolutely perfect in a mercedes (no frills, just quality). You'll learn that, unlike home audio, in your car as long as you get good components, the install will make or break your system. Pick up some good parts; focal, mbq, nakamichi, ppi, phoenix gold, etc, and get a comprehensive install done at a trusted audio shop.