If you really wanted to go real world, 99% of all gamers have video cards slower than a 9600 pro, as well as most if not all of them run at 1024X768 or lower.
Don't go comparing a benchmark between a 7800gtx and another card unless you are talking about a MINIMUM res of 1600X1200.
OF COURSE the X850XTPE could compare to the 7800gtx if you compare them to each other in benchmarks where both video cards are not the limiting factor, heck a geforce 2 would go toe to toe with a 7800gtx sli config if the game was old enough and the details low enough.
Why bother comparing the state of the art with the old on something that the old can already do easily??
If you want to test pure video card power, run a game at 2048X1536 with 4XAA and I can bet that one card will lose by more than half.
Hint: It will not be the 7800GTX.