I'd be more than confident that it would be equal to or less than the power draw of a X58/W3670!!
Have you done any power draw tests on the system?
The servers I was testing yesterday was a bit interesting to me, the newest one I have, was a quad core and the power usage on idle was about the 75w mark, when the fans sped up to maximum, it was nearly hitting 200w!! That's without the CPU under load as it was going through the bios checks.. I was stunned but still.. I'd hate to think what it's going to be like with dual 10C 20T CPUs in there and filled up with SAS drives for storage
I wonder if it might be something around the same as my 5960X with the Ti's running FAH