well, my 5 cents, i am using hackintosh with a 460 for gui and gpu, and my renders in 1080p prores are more fast than real time, if you need some test tell me.
I am running hackintosh also 10,6,6 and I did the normal install and when i do the render from canon dslr 1080p I get a warning sign H.264 encoding on Mac32 doesnt support resolution beyond 1440×1080.