I do not believe that a 750k will bottleneck a HD 7950. It isn't as bad as a lot of people are making it out to be.
Sure the i5 would be considerably better but it is 2.5 times more expensive than that Athlon.
Oh I don't doubt the 750k would run "ok" with the 7950 and the 750/760k would probably be my budget gaming CPU of choice. All I'm saying is in a system with a 7950 and 750k, the CPU is going to be the bottle neck in most modern/up-coming titles.