1) For the most part, its rock, country, electronic music. I like clear high's and deep low's.
2) I listed for my mood. I typically listen at an average volume, but do like cranking it up from time to time.
3) Most my music is mp3/Zune format plugged in through the aux jack.
4) Budget isn't extreme. I don't want to get in to custom enclosures, etc. Ideally would like to do it all for under $400.
The only reason I might do the local shops would be to have them install it if I'm feeling lazy. I typically havent had much luck there and have put together most my stereos through online purchases.