I find that I still need both a music manager and a simple music player, in case I want to test a file outside of my collection. In my opinion, the best XMMS lightweight audio player is still XMMS, or any of it’s clones like BMP or Audacious. I prefer the latter. But none of the XMMS clones follows your GTK-theme, so it tends to be rather ugly. Good thing is, they also support winamp skins, and there must be millions of those. Most of them suck. Very rarely, they look polished, professional, and stunning.
Case in point. I especially like the rounded corners, and the little orange cross. This looks great on a default Ubuntu install.