i really dont think you would have very much performance problems at all.The agp 4x is good enough for anygame out now.You might notice some problems sometime in the future though.ANd also you really should have gotten the 9500 Pro cause it is a very different and better Graphics card than the reg. 9500.
I agree with payniel. There won't be any problems in the near future, but maybe in a while... might be worth it. You can always upgrade later if you decide you want the 8x.