I've just accidentally stumbled upon BMP.
No, I don't mean .BMP as the Microsoft bitmap image format, or any other of this acronym's meanings. BMP in this case stands for Beep Media Player. It's now a two-year old project, which forked off the more known XMMS player. The main differences being that it's using GTK+ 2 and trying to not be monolithic.
Well, it's not finished yet, but it's very much usable and looks pretty good too! I think it's worth a try, if you're a XMMS user.
…But I'll rather stick to amaroK myself. It's a completely different league, if you ask me. :]
Update: All links were dead, BMP project seems to be as well, so I didn't migrate links.