On the upside, threw some MP3s on my amiga and I was surprised. Sure, its not amazing quality but it still sounded pretty good (Iron Maiden's Powerslave, if anyone was wondering)
If you want amazing quality, do a quick convert to ADPCM4. I've played them at 230kbs, 27400khz. (on a double scan screen, they will play back at 56khz). It takes about 10 seconds to convert an MP3 using 'quick media converter'.
Listen to 'Lightshaft' and 'we come in peace' by Demo group elude for a qality comparison. The compression is quite good, and they can be zipped/lha'd further.