You finish building the rig OP?
If you're still unsure about the video card, I can tell you that AMD is alot faster than Nvidia in OpenCL, for whatever reason. An R9 Fury, in particular, will chew through fancy vapoursynth denoising, scaling, and motion interpolation like there's no tomorrow. And if you're looking for the absolute besy quality processing done in a sane amount of time, that's exactly what you want.
Nvidia cards have a huge advantage in Waifu2X-caffe if you ever plan on working with animation.