True, that's another good point. Talking of plugins for other music formats, the Oldsk00l MOD Player Plugin for Winamp provides much more accurate playback of Amiga MOD files than the built-in Winamp MOD player. Absolutely recommended and essential if you like Amiga (crack intro) chiptunes. Hasn't been updated in ages but still works fine for me.
It also supports some other Amiga formats, you can find it at http://www.rift.dk/page.php?1