Budget?
If money is not a issue then just get an i7-5960x, overclock it to 4.2GHz, and call it a day.
If you want something that doesn't cost you the equivalent of an entire mid-tier gaming PC, get an i7-5820k. It has two fewer cores than the flagship 5960, but at a third of the price, and you can still use the X99 platform with it. The six cores will help AE performance over the non-HEDT i7 cpus as well.