Seriously, there is no need to buy a $500 card. You are better of saving $150-$200 buy buying a midrange card that will still last you 1 - 2 years.
But for the X800 XT vs. GeForce 6800 Ultra, when it really boils down, for all general purposes, it is basically a draw. Other than a few FPS in either way based on the hardware setup, it all comes down to your own personel preference. I have seen many benchmarks where they are equal, and I have seen many benchmarks where one card will out perform the other bay large margins. If you are looking for actual results, you can find them either at sites like www.hardocp.com or www.tomshardware.com, both are reputable sources.
naa, doesn't matter which card does better, we all like ati =) and if I was working right now, I would have the X800 already. I find a need to have a 500-600 dollar card in my machine because the more power in your computer, the better! I want better graphics =)
i would pick the x800 xt because ATI has always been my Faviroute. Ill always stick with ATI beause ive had no problems up to now with there cards at all. BUT everybody has there own favirouts.
I chose the X800 because to show my support to ATI, even though the X800 is less technologically advance compared to the 6800 and ATI is a canadian company.