I found not one mp3 player that could play all the mp3s that I had on my smc. That's why I went for OggVorbis. First with Yogg, now with SvOrbis. With foobar2000 you can batch-convert all mp3s you want on GP32 to a smaller size, so that more music will fit on one smc.
Greetings,
SvOlli