All,
I've completed a beta version of a MAD plug-in for Winamp. You can download it from the MAD home page:
http://www.mars.org/home/rob/proj/mpeg/
It currently lacks streaming support, but will handle all *.MP[123] files.
One of the goals of the plug-in is to provide 24- and 32-bit output if your soundcard supports it. However, it is not known whether any Winamp output plug-ins (including the Nullsoft waveOut plug-in) support any resolution greater than 16 bits. I don't have the necessary hardware to test this, so I'm hoping to get feedback from anyone who can try it.
I will be releasing source for the plug-in along with the next regular source code release.
Cheers, -rob