I have this card and am pretty happy with it. I was able to unlock 4 extra pixel pipelines for a total of 16. Unlocking the pipes makes it equivelant to having an X800XL. I can run CS:S at 1600x1200 and I think I can run BF2 at 1600x1200 with medium textures (only 1GB of system RAM) and high everything else. I haven't tryed it at that resolution in BF2 much yet. I'm running a Pentium 4 2.8C @ 3.5GHz.
What are the difference between an X800GTO and a X1600Pro? I am rather confused on which is better. Which one would give btter performance?
The X800GTO will be faster than the X1600Pro. The X1600Pro has newer features like SM3 but from what I have heard it isn't really fast enough to use it very well. Right now only a few games use SM3. If you play HL2 or CS:S or BF2, I don't think any of those games use SM3 or the newer HDR. The X800GTO will do the HDR that is used in HL2/CS:S.
You probably aren't expecting your AGP system to last too many more years as a gaming system so you might not care about SM3.