You should be ok with the 7950. It may bottleneck a little but it would still be much better than the 550ti if that is what you are still using from your signature. While the original Phenom's are not quite as good as the Phenom II I think you will be quite happy with the 7950. I am running one in my rig and it is very very good. I did not update my hardware in my signature yet but it is better than my Crossfire 6950's and I am only running one 7950.
To help clarify your options, run these two tests:
a) Run your games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely cpu limited.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 50%.
This will simulate what a lack of cpu power will do.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
set to 50% and see how you do.
If your FPS drops significantly, it is an indicator that your cpu is the limiting factor, and a cpu upgrade is in order.
It is possible that both tests are positive, indicating that you have a well balanced system, and both cpu and gpu need to be upgraded to get better gaming FPS.