IMHO, besides the PowerMac G4 being cheaper then the G5's, I wouldnt buy old technology. Remember that going from 32 to 64 bits is already a big jump in tech, specially when you compare the technologies that both computers have ( PCI-X, AGP 8X, That massive Bus speed, Serial ATA, etc etc etc). If you cant get a Dual 2Ghz G5, do your best to get the 1.8Ghz Powermac. Thats what i would do.