I just built a new machine and used a CORSAIR CMPSU-450VX 450W ATX12V it has amazing reviews and runs at a pretty cool temp in the case I used. I guess just putting my vote towards a corsair PSU and good luck on your project I really can't wait to see it completed. I'm also going to guess that your os9 software doesn't run well under classic or your accessories do not work under classic?