But, other than that, everything looks fine. I'm not sure (at this time) how the PCIe SSD affects the PCIe lanes in the x99 platform. The Z170 platform has enough PCIe lanes in the chipset to handle the SSD without affecting the lanes from the CPU.
The Haswell-E CPUs provide a ton of PCIe 3.0 lanes themselves (in the case of the i7-5820K, 28 lanes), but the X99 chipset provides the same PCIe connectivity as Z97 and earlier: still only eight PCIe 2.0 lanes.
On a Z170 system, you've got only 16 PCIe 3.0 lanes coming from the CPU but 20(!) PCIe 3.0 lanes coming from the chipset. The latter are limited to the speed of the DMI 3.0 link, though, which I think means they are functionally limited to 4 lanes per device.
An i7-6700K is another good choice, but I think an i7-5820K is worth the marginal extra for this sort of workload. The CPU's 28 PCIe 3.0 lanes are enough for a single video card in 16x (or two in 8x/8x) and still leaves 12 lanes for up to three more PCIe devices in 4x mode without relying on the chipset. Hell, you could put in a third GTX 980 Ti and still have the 4 lanes needed for the SSD.
Edit: Rumors abound that we may see Broadwell-E, a new generation of high-end Intel CPUs, launch sometime this year. No official word, but it's something to be aware of.