A bit of improvement in few games. If you already own a fx 8350 than keep it, but if you are getting a new cpu getting a fx 8350 isn't a good idea. I had fx 8320 and I had oc it to 4.6 ghz could have overclocked to 4.8-4.9 ghz I am sure about that. But it was bottle necking in many games. Shifted to i5 6500 it has much better performance, I felt I upgraded my GPU. Unlocked i7's give seriously good performance.
If you have the cpu oc it to 4.8ghz and it will be Ok for 4k gaming.