It's more complicated than it seems, there's like 6-7 models of the 8800GT 512. Check the XFX website, some are not PCIe 2.0, some have DDR2 vs DDR3.
http://www.xfxforce.com/web/product...seriesId=730995&productId=1558693#popupLarger
http://www.xfxforce.com/web/product...seriesId=730995&productId=1558693#popupLarger