Not really especially when a 7850 is with a pentium g series cpu there will be like 30-40fps less due to the slow cpu.
The Athlon is a bit slower than the FX 4300 but a lot cheaper and the Pentium is a bit slower than the G2120 and again a lot cheaper. http://www.xbitlabs.com/articles/cpu/display/fx-8350-83...
As you can see, the Athlon is clearly the better choice and it will NOT bottleneck your HD 7850 in any significant way.
Remember than the card they're testing these CPU's with is twice as powerfull as yours, so the difference you'll see from upgrading from the Athlon 751 to a Core i5 will be twice smaller.