Everyone's missing a trick here. GTX Titan with nothing more than a bios refresh - TDP of 300watts, unlockable voltage to 1.21volts (more if the base hardware spec is within tolerances) and better cooling, a la ACX from EVGA.
Titan has a lot of leg room. Alternatively, I said before, a GTX 780 with it's standard 3GB, the same cores as a Titan with mentioned bios revisions. Let the AIB's throw in custom components (VRM,s etc) and you have a GTX 785 or allow the AIB's to customise the Titan base product and Nvidia remove the DP compute to keep the K20x crowd happy.
Yes, Nvidia can easily up Titan's performance by 10-15% from Bios alone. Let partners play with hardware components and it's up by 15-25%. (Look at Radrok and Khemist's Unigine Valley scores, about 110-115 fps ave on 1080 4xAA Ultra quality).