I was initially worried about this too, as I've read others using the X10DAX mention using a V3 chip to perform the bios update. Thankfully my X10DAX supported the E5-2690 V4 out of the box. The bios version is 2.0 with build date of March 9, 2016.
The (Pascal-based) Geforce GTX Titan X was just announced, so that is the main video card I'm considering now.
At idle I'm measuring ~97 W. However this is without a powerful video card.
The 6700K is a great chip. I agree it can be tough to decide between i7 Core and Xeon. The Xeon E5-2667V4 sounds pretty close to the 6700K specs but it costs about 6-times more, so not a very good price/performance unless you need a ton of RAM or ECC. I debated it a bit myself, but for my application I decided the benefits of using 2 x E5-2690V4 outweighed the higher cost.
Sure - software development is my primary profession, so I'm using the machine for several things related to that: running containers and virtual machines, doing software scalability testing, and some data processing.
EZ-Watt shows it using ~350 W under full load right now. I still haven't pulled the trigger on the 1080 as I'm debating going with a consumer / gaming, or professional video card. Once the video cards and storage are finished I'll update the max watts.
Actually an 8800GT. I'm using it as a placeholder until I get the final video card situation sorted out.