I decided to replace my HiS ATi Radeon 5450 1 GB 64-bit DDR3 on my current system with an older PNY Verto 9600GT 512MB 256-bit DDR3. As much as I liked to love the ATi, I felt that it was slow for my needs and it was a little too fragile for something as unpredictable as a Hackintosh. While the ATi can do DirectX 11 and was a cool, quiet (fanless) graphics card, the framerate I was getting from it was too low, and I know that it was the bottleneck to my system. I also felt that this was one of the reasons the Sleep ability on my current system was buggy - sometimes after Wake from Sleep, Bluetooth needs re-pairing with some devices (rarely) and sometimes, my WiFi card does not get detected.
So here I am, with my PNY Verto 9600GT 512MB 256-bit DDR3 installed. The replacement was uneventful, with the only step I took was to remove the Ati5000 kexts and other related kexts from my S/L/Extra folder, and edited com.apple.Boot.plist a little bit. I installed the NVIDIA update from tonymacx86, rebuilt caches and repaired permissions, and after reboot, everything was working with full QE/CI. I tested with framerates with Cinebench and received about 3 times the framerates I was getting from the ATi card. I tested all my photography editing software, as well as Starcraft 2, Civilization IV and Simcity 4: Rush Hour, and everything played better, faster and nicer. As far as I can see, there was no difference in color rendering or detail to my desktop or to any programs I ran.
I plan on testing Sleep and Wake from Sleep with this 9600GT, but I will do this after I update to the new 10.6.8 Snow Leopard from Apple.