bit-tech just published a comparative review of AMD's ATI Radeon HD 2600 XT GDDR4 and Nvidia's GeForce 8600 GT A quote from the article:

We've evaluated performance across three resolutions in six games against six other cards. Additionally, we've also tested HD video playback with both Blu-ray and HD DVD discs and evaluated power consumption. If you could post a link on your site that would be very much appreciated.

AMD ATI Radeon HD 2600 XT GDDR4 vs. Nvidia GeForce 8600 GT Review