The card comes in three flavors; I bought the lower-end X850 Pro for about $250. The other two models are the X850XT ($390) and the X850XTPE ($450). Please note, this is the AGP X850, not PCIe and these prices are quoted at the absolute lowest I could find them at.
I overclocked it as both an XT and the XTPE so I could benchmark each. Here are the benchmarks showing the boost in performance over the stock pro.
As you can see, the greatest boost in performance comes from opening up the per-pixel pipelines from 12 to 16, this is the difference between the X850 Pro (12 PPP) and the X850XT (16 PPP) since each of these run at the same Core speed (220 MHz) and Memory speed (240 MHz).
Regardless, moving up from the XT to the XTPE still shows a noticeable performance gain. While still running at 16 Pipelines, the core speed gets boosted to 240 MHz and the memory speed to 290 MHz.
The core temperature when running as the X850 Pro was about 30 degrees Celsius. After overclocking it, it jumped to about 50 degrees Celsius so then I went in and forced an overclock on the cards fan from it's default of 50% utilization to 90% utilization. This brought the temperature down to around 37 degrees Celsius. There is only about a 1-2 degree difference between when running it as the XT or the XTPE which I thought was interesting since I expected to see more of a difference in temperature between running as an XT vs an XTPE with the additional MHz.
It seems to be pretty stable so now I'm going to go ahead and run it as the XTPE for a while and keep monitoring it's temperature. If it starts getting too hot or unstable, I'll probably order a third party aftermarket heatsink and fan. If you look at photos of the X850 Pro and then an X850XTPE, you'll notice a big difference in the stock cooling between the two which makes me nervous to run the card as an XTPE on the stock Pro cooling fan.
This was my first video card overclocking, and I'm quite pleased with the outcome!
Thanks for all the help guys!