I've played mp3s on my 54 MHz A2630 with good results (Stereo + Paula14C) using mpega.library but subject to the following limitations:
- Use Integer 020/030 version of mpega.library
- Use 1/2 playback rate (22 KHz)
- Play from the shell (GUIs waste CPU time and won't allow the large buffer size needed)
- Set buffer size to at least 75% of the mp3 and WAIT before playback begins
