I'm going to be buying the A4 real soon. However, because I am an audiophile I need to have the best stereo system possible. I will definitely be getting the higher-end stereo system (Bose). I see it comes with a sub. I listen to a lot of techno/trance so bass and highs are important to me. What I want to know is, how does this sound? Is it powerful? And, does it have an amp? If I want to upgrade (throw in an amp, stronger sub, different head unit, etc.), can I trust someone like Circuit City or BB to do it or should I have the dealership do it? Thanks for any and all help!