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.