As much as people hated it, the 2900XT was faster then even the x1950XT. 2900pro might be around the x1900xt? Which I think was around the speed of the 3850? 4650 or maybe 4670 performance? In terms of which 6 series card I'm guessing a 6670 maybe? Might even be the 6570. Tons faster though I'm sure you knew that.