The 7950 will run better with the i5 but will run ok with the 750k. However, if you start running CPU-intensive games, the 750k will drag down the performance and cause a bottle neck. The 7950 will not bottle neck a 750k.
The 7950 has no issues running bf3 and 4 from a graphics stand point, however the 750k will probably hold performance back a bit from a CPU stand point. Especially when you get into playing bf4 with 32-64 players online.
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.