wow, a bit off there. The 9700 is older, but it is an 8 pipe card and better than the 9600. I still run it oc'd and it rocks. It was ati's flagship that was the first of any card to support sm2.0. Came out against the geforce4 ti and stomped it. The 9800pro is just an upclocked 9700pro (minor arch changes). Testament to how rockin that architecture was is that nvidia could not beat it until the 6 series! (*cough* 5 series did ok, but just stumbled on pic quality and frames in dx9b games *cough*) Perhaps ati was resting too much on it and that is why they are playing catch up now?...
anyway, the 9600 is a completly different chip. the 9500 was a pared down 9700 but the 9600 is just different and is a 4 pipe card. It was the first ati card on the smaller manufacturing process and did not need the extra power connector like the 9700/9800. It performs much lower than the 9700. (this is assuming we are talking about the pro versions of all of em) Look at the agp charts on tom's. I have a friend with a p4 2.8 and 9600 pro and cannot compete with my athlon2700 with 9700pro. (proc is obviously better but gpu much worse)
either way, I agree with the above that the gpu is the issue. It is just plain old. (I am finally upgrading my system) I have seen my friend run FEAR, but at 800x600 with nothing turned on. Mine will do same resolution with some stuff on. (no soft shadows or AA) These cards have just finally hit the limit. (i assume PoP is similar to newer games, i have never played it) Time to upgrade.
The cpu is also an issue, but much less than the gpu. if you are going to upgrade I would recomend doing both, which would mean new mobo and prb ram too. (depending on proc)
The versions of the game performing different could be coding differences in game or drivers.