"Have they done a Yosemite hack yet? I too have a 1,1 as my desktop, upgraded it to 10GB RAM and put a GTX550Ti in it this year. Runs everything I throw at it, still just on 10.7 though."
Yep - Theyve been busy !
Mavs hacks have been out for over a year and were quite involved.
They've really errr, streamlined the process now. Not that I recommend this type of thing.
Mines like yours probably - runs smooth as silk. I put the Radeon 5770 in - yeah I'm a cheapass !