Titan X = 3072, Titan Black = 2880, that to me, is not really the big difference I was hoping for here.
The Titan Black is essentially available today for about the same price...
And on top of that - why would I want to buy a Maxwell card NOW, if there might be the new Pascal generation of cards around the door (which according to nVidia) will sport 10x the power of Maxwell - although only for deep learning, but why couldn't that be used for rendering as well?