We already wrote that the Radeon HD 2600XT can't keep up with the Geforce 8600GTS, but it can probably performsas well as a Geforce 8600GT.
The Radeon HD 2600XT will be selling for $149 which is some $20 less than the cheaper 8600GTS. Usually the GTS costs up to $200+, but we found one for as little as $170 from MSI and it is passively cooled. You can get one here.
Most of people expected a $199 price tag for the 2600XT.
Performance wise the Nvidia Geforce 8600GTS will win, but it is more expensive to produce such a card. ATI makes more money per card, at least on this generation as its chips are smaller, but we recon Nvidia will sell more.