As we reported it previously, one can flash a PC GeForce 8800 GT with the corresponding Mac Edition ROM, saving a substantial amount of money. The entire procedure is available as a new article: Use a PC GeForce 8800 GT in a Mac Pro Rev2.
Some users have immediately tried to flash a PC GeForce 8800 GTS 512MB, and apparently with success according to a report from Macrumors forum. However, it seems that the card does not work anymore when running windows on the same computer.
Before going further, let's see the difference between a GeForce 8800 GT and a GeForce 8800 GTS. Based on specifications, the GF 8000 GT and GTS featuring 512MB of VRAM are very similar. They have the same architecture, the same memory bus; however the GTS model is faster.