The Best Music Player App on Android?

Hey guys,

So I've finally got round to turning my old S2 into a little portable sound system (with the Cambridge Audio Minx Go for anyone interested).

I've never worried too much about my music player when listening through headphones...and to be honest I don't even know if the differences between them are that great (can they differ in sound quality or just UI etc?).

Anyway I'm looking for suggestions (free or paid I don't mind). Something with a good and usable UI, and good features but nothing too anal I guess. Sound quality is the biggest thing, though like I said I don't know if that's relevant.

I won't be streaming or listening over wi-fi, this will be playing off local media. And I listen to everything from classical to drumn'bass to folk to hiphop...so I need something that I can set up and leave without needing to change settings for each type of music.

Thanks!

EDIT EDIT EDIT

I forgot one of the essential requirements...it must be able to crossfade tracks (ideally with a number of seconds option). I listen to a lot of pre-mixed dance music of shuffle so this is really important, and aside from that I just prefer listening to crossfaded tracks so everything gels seamlessly.