I currently play most games at a mix of medium and high settings at 1280 x 720 resolution.
My system's hardware specs:
- AMD Phenom II X4 965 BE
- ASUS Radeon HD 6770 1GB GDDR5
- 4GB G.SKILL Ripjaws X-Series DDR3 1333MHz RAM
965 BE is still pretty solid and capable of gaming plus it OC's very well if you need a cpu bump. If anything drop another 4GB of ram into that thing and upgrade the GPU (6770) isn't really all that powerful anymore. Plus the new GPU and RAM will be swappable when the day comes the 965 can't hack it anymore.
If you have you hands over those 3 PC`s you can run PassMark 8 on all.
When you have finish with test you can save you score like Base Line.
You can import those Base Line on one of them and You`r done ,,,,, you will see % of difference of the PC`s.
If you don`t have hands over them you can check this Benchmarks - tested with PassMark and uploadet for information :
Intel Core i7 960 @ 3.20GHz - 6020 score
Phenom II X4 965 - 4321 score
FX-8320 CPU - 8227 score
On other hand :
You ask abaout Gaming performance but you did`t give a GPU Model you have/ask ?
Edit : ups i sow it now you have 6770 - you have VGA Bottleneck
If the CPU is above some point it`s all about VGA speaking of Gaming.
In other words if you have for example VGA ATI HD 7970 and 2 x Core CPU you gonna hit the CPU Bottleneck .....
But if you have 4 x Core CPU you gonna hit the VGA Bottleneck of you system.
To be 100% sure you gonna play some game you can use this web tool :
You gonna see where is you System with specific game - minimum recommended and optimal performance ....
Edit : you can see Upgrade options too - VGA and CPU in the Optimal test section is recommended for Optimal Gaming
You can pick the "HUNGRIEST" game on the market now - Crysis 3 will be the right pick i think for testing in canyourunit.