As Cav said, the ATI 'block dot' issue was due to older video card drivers. Use the driver of the same age on an NVidia card, and the game will crash to the desktop.
Darkish, the X800Pro actually uses less power than the 9800Pro does and runs cooler, but power is an issue for any modern day video card. Still, a modern day system with these video cards will need a good 480W, or better, power supply.
Once you get into the X800/6800 territory of performance, you can consider it a nice long term investment as there is not a CPU available today, which will push those cards to thier limits.