Hmm. So would I be better buying a 2009 4,1 or going with a later release Mac Mini?
If you already has a 7950, it is possible to get a 4,1, flash it to 5,1, and install a X5677 to make it a decent gaming machine for $500.
However, I am not sure if you can really benefit from it, if the low FPS of your game is software / setting issue.