Dunno man, I've heard $10,000 car audio systems that sound like garbage compared to my $200 Swans M200. Unless you spend a whole hell of a lot of time in your car, I might look into a desktop speaker system instead. Cars are one of the worst conceivable acoustic cesspools imaginable -- glass, leather, carpet, plastic, and wood all over the place and in all sorts of odd shapes and dimensions, not to mention the constant distraction of the engine hum and the sounds of the outside world.
Hmm, guess I got off topic here -- the only car audio enthusiast forums out there probably tout Bose anyway.