The GTX 650 Ti - WORKING!!!
After messing about trying to update my 10.6.8 to 10.8.2, all while upgrading cards, I started over-
1. GA-P55M-UD2 mobo, with NVidia GTS 250 card- Installed Mountain Lion with provided DSDT, no biggie.
2. Installed NVidia CUDA drivers, as mentioned previously...