When streaming, the FX 8350 is your best choice. Yes, best. It soundly beats the i7 3770k/4770k...even the intel 6 core CPUs.
This is because it has the extra cores available that aren't being used by the game, and can thus be used to capture and compress the video stream.
When just gaming, it performs about the same as a good i5 or i7.
Just verify it is supported on your motherboard before you purchase.