I have been with ATI RAGE 128 GL/PRO for years in OS9 with "acceptable" behaviour, but on OSX RAGE is really low end. Tiger and Leo demands not only Quartz capable cards (any card from RADEON and Geforce MX2) but CoreGraphics cards (From Radeon 9600 and Geforce 5200), having bad performance on Quartz only cards for keeping that eye-candy OSX look that Steve Jobs said "you have to lick".

You pay CPU cycles on OSX for the eye-candy. All DAW OS9 users have "half" the power on OSX than on native OS9 for this shit. I use shadow killer on OSX http://www.macupdate.com/app/mac/6428/shadowkiller-x and that "helps" performance on RAGE 128 setup to be "acceptable"

beside the fact that this is a Mac OS 9 forum ... the worst you can do with a PPC G4 is to use it for audio in OSX.

Yes, but some features (as elastic audio on protools) are only on OSX versions. It could worth some users to edit with those OSX only tools and keep mixing on OS9.