Just wanted to share my experience. Looks good! I put up a rig with Core i5-4690, 16GB RAM and Nvidia GTX 1070. I have movies on a separate box, accessing them from this rig via NFS share. As you can see below, the rig can easily handle simultaneous full hardware decoding and encoding of 5 videos where each is 4K video, transcoded to 1080p video (CPU is only doing Audio decode/encode). And there is plenty room for more simultaneous transcoding 
