I tried to get the FMV card working for MP3 playback, but I could never get Amplifier going on the system. It kept crashing with a Guru.
Assuming you can get Amplifier operational, go to the Config menu, the decoding tab, and set everything to hardware. Enter cd32mpeg.device, unit 0 in the now-unghosted box.
I don't know if other players can hit devices directly, so Amplifier may be the only option, as cd32mpeg.device is ROM-resident.
