Xeon E5-2697 v2 2.70GHz , Best hashrate among the bunch.i7-4960X 3.60GHz, or Xeon E5-2697 v2 2.70GHz, or i7-4930K 3.40GHz.
But it is one power hungry CPU. It depends on how much you pay for power.
My be other CPU produce less hashrate but more profitable .
I mine with a E5-2696 v2 temporary to stress the system now, future usage for the machine is run Windows 10 Creator .