Noatun comes with a number of visualizations, including one (not shown) which jostles all of your windows around to the music!
There are a number of interfaces available for Noatun, including one that can load GQMpeg skins, and one that can load WinAmp skins.
The GQMpeg interface (Kaiman) supports shaped windows, just like GQMpeg.
You can configure Noatun to search for song lyrics over the Internet.
Noatun trying to pull up Beastie Boys lyrics via a simple Google search...
You can apply effects to the audio, including voice removal, enhanced stereo, pitch adjustment. You can also write the audio to disk.