Be sure it has the latest BIOS, which supports BW-E.
Asus and Gigabyte MB's have problems posting really early sample ES chips, take that in mind. For example, my Gigabyte X99 UD3 w/ latest BIOS doesn't want to post anything on my 2690 V4 (QHVE5) but my 2630 V4 (SR2R7, but is a later ES chip)
You can take a gamble, or just ask the seller for accurate info (sellers usually don't answer the questions, idk why)
Some good options with optimized frequency:
14-core: E5-2690 V4 ES @ 2,4ghz (3,0ghz all core boost) (550 dollars)
8-core: E5-2667 V4 ES @ 2,9ghz (3,0ghz all core boost) (350 dollars)
12-core: E5-2687W V4 ES @ 2,9ghz (3,0ghz all core boost) (around 680 dollars, out of stock)
Hope this helps!
Thank you very much I appreciate that
I think i will gamble a little bit with the 2690 v4 ES.