I am not at all convinced with the results from the Tomshardware review. The XT800 XT falls behind on a lot of benchmarks but does catch up with the 6800 Ultra due to its high performance using AA and AF image enhancers. When the XT800 XT does "outperform" the 6800 Ultra it is only by a very small amount.
The Hexus review
shows a much better result if you are a fan of ATI.