What kind of improvement in frame rate did you get.. 2, 3 frames more a second? and if I'm not mistaken, isn't the x800 Pro an AGP GPU with 256 Mb of DDR.
My Graphics card is an x700 Pro PCI-express. Not to sure of the difference between mine and yours (graphics card that is)?
I'll deploy 2 new machines later today and compare an AGP versus a PCIE and see what kind of results I get...
... only using 3DMark2005