I just ordered an OWC Mercury Extreme 1 GHz CPU upgrade & a SuperDrive for my old G4/500 minitower. It already has a Radeon 9000 graphics card & 768M of RAM. I still have to put a larger internal drive in it – the old 80G drive died a few months ago & I replaced it with a 45G that I removed from another system.
My server is running very fast now with 768M of RAM.