[Marcus Herrick] “My question is, will the 6 core be enough CPU power for HD grading?”
The CPU cores are primarily accessed for the User Interface and codec processing. The image values for correction are computed on the GPU/CUDA cores provided by your GPU array. In that respect, unless you are trying to deBayer RAW media, the number of cores starts to become irrelevant.
In your case, multiple GPUs will help only in the instance where you start building complex node trees with other processes over-layered, such as noise reduction, blurring, and alpha channel compositing. I have seen YouTube tutorials that feature power-supply splitting to run multiple GPUs, but whether something that is technically possible is advisable depends on how long you want your equipment to last. Also, if you intend to house all your GPUs in the chassis, eventually you will run into a) cooling issues, and b) the reality that the #3 and #4 PCIe slots are not x16-lane.
jPo
“I always pass on free advice — its never of any use to me” Oscar Wilde.