I am in the process of upgrading my PC's graphics card from a Radeon HD 6450 to a 7950 or a 7970.
My processor is a AMD FX 4170, i understand that there would be a bottleneck so would it be worth paying the extra money for a 7970 over a 7950?
I'd recommend HD7950. They are $300 while HD7970's are $400. Assuming your resolution is 1920X1080 or lower, the 7950 will be fine. It can be overclocked quite a bit for performance nearing or surpassing the 7970 for the 7950 tends to overclock better.