I've heard that Pro's are just underclocked XT's that couldn't pass stress tests at XT clock speeds. Same goes for 6800GT vs Ultra. I'd go for the Pro and if you crave some extra power you can always use Powerstrip to turn the clockrates up, though an aftermarket cooler may be required.
depends on the kind of games yer gonna be playin, and at what resolutions etc. x800 xtpe is a badass card but has a 500 dollah price tag. the x800 pro should be able to handle any new game just fine for a while and at higher resolutions than say a 9800 pro. but I can vouch for the 9800 pro still kickin ass cause I have one and play all of my games at 1600x1200 just fine. im waitin for the nforce4 boards to get a revision till I buy one and then ill be running dual vidcards with the SLI.