I had 4 D0 CPUs on EVGA boards (X58 SLI and Classified E759) and none needed more than +200 for 4GHz Uncore. You seem to know how to do your testing, but many DO NOT.

BTW, Corsair is being conservative with their XMP profile to be sure those GT can be run at almost any system. I also own Corsair GT ram (2000 CL7) and it's the best ram i ever had! I could run 1.6Vdimm and 1.324Vtt @7-7-7-20 1T RTL 53-55-57 fully stable with my Xeon on water. It's a great cpu as is my 950, but I really cannot understand why most of the XE cpus need more voltage to run same speeds as good 920/W3520 cpus.