"file format unknown" is exspected, because it is in fact unknown. but it depends where you get the message
in toast for example, it is normal, that it will report "unknown". just dont change the sector size, press mount, and it is there.
actually, in my personal experience, mounting akai disk in the mac os never was useful for anything else than creating a backup copy. maybe some of you remember the "akai cd reader" or the akai import tool from ik multimedia. both software are really a piece of crap.
CDXtract all the way, in OS9 and OSX! there is no other. directly importing from akais (such as the logic samplers allows) is in practice more work and more difficult than converting the whole CD.