Two words:
LOUD and CLEAR.
I think I'm the only Dad in the school with a pair of 12" subs in his minivan instead of a stroller. The stroller stays in the garage.

I love when the Mom's at school give me the evil eye for playing "Get Low" too loud when I'm dropping my boys off...it's great
Although I enjoy other's reactions, I just enjoy my music loud and clear, whether it's on my
PC, in my car or in my home theater.
As for music genre, I like neo-soul the best,, hip-hop, some rap (especially 80's and 90's), urban, select hard rock stuff (Coldplay, Nickelback), some classic rock (Floyd, Eagles), the occasional trance/techno/electronica, classical (I like strings the best...Taffelmusik's version of Four Seasons is OUTSTANDING; I like Tchikovski for his aggresive compositions too)...pretty much anything that's well arranged and produced, not stuff that was thrown together to make a buck. Oh...and stuff with lotsa bass puts the F.U. in FUN when I'm in the mood
[EDIT] I know
exactly what you're talking about JE ... subtlety is an excellent way of describing it...my car setup (currently) is better than my home setup, and the intamacy of that setting brings out amazing detail, despite ambient noise. I'm running a Phoenix Gold amp up front to a pair of MTX separates, and to the rear speakers for fill,, and an Alpine mono-block to a pair of 12" subs in the rear hatch. All controlled by a Panasonic head unit with electronic E.Q. and x-over. In the next couple of months I'm upgrading my HT setup so I can really enjoy my CD collection.