Xbitlabs has a very good article about your very issue, they tested QX9650 vs i7 920 with GTX285 and GTX295.
http://xbitlabs.com/articles/video/display...285-gtx295.html

I quote from the article:
"I have also found out that the new platform with a Core i7 processor and fast memory is ahead of the Core 2 Quad platform in most of my tests at the default CPU frequencies as well as when both are overclocked to 4GHz. The Core i7 enjoys an impressive 35-40% advantage when not limited by the graphics card. The tests suggest that the new platform is worth the investment, and you can even hope for further performance benefits from SMT technology in the future."