Well, I was just doing the same thing (trying to using my FW Audiophile on an iMac Indigo 500MHz w OS9.2.2) and seems that I should forget to get it working...
I will just try to be sure, but I suspect that will not works.
This device is really strange, I've got several problems on making it works with certains FW controllers in Windows 7, but using Windows XP it worked with the same "bugged" controllers.
I confirm that if the device doesn't boot properly when the headphone cue led remains off, but sometimes it worked also with that led off.
However, a couples of days ago I've found the drivers on the M-Audio site, I don't understand if any one of you guys has already tried the official drivers. I think that this will be my first shot.