I'm going to be a dick and recommend not using Winamp. You could try Songbird, Play, or Cog.
Songbird: http://getsongbird.com/ Cog: http://cogx.org/ Play: http://sbooth.org/Play/
Obviously, VLC works as well, and there are Xiph decoder packages that should make FLAC and Vorbis files work in iTunes, if you're into that sort of thing.