The 7.9 is a typo, it should be 7.6. And the 2900XT does indeed perform well in 3DMark06. We're not the only site to show that. Even our original article on the 2900XT demonstrated that.
Nothing is wrong with the 7800GT. It's just that it's an end of life product. The pricing on the card is absolutely horrid. Newegg has two new models, both of which cost almost $300. For $300, you can get a much better card.
The point of testing with such powerful hardware is to highlight the differences between the various video cards, in this case we know the performance differences can reliably be attributed to the video card. If we tested with systems that had other limitations, we probably wouldn't find out which card was more powerful.
mujeeb1 - With respect to Prey, you won't need much in terms of a CPU. Our Athlon FX-60 clocked down to 2GHz moved frame rates down by little over 10%. Which basically means, short of buying a bottom of the barrel $90 CPU, you should be fine.
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