How much does ram speed matter? Have you checked benchmarks? I thought it was relatively inconsequential, but I could be wrong. I'm using a single 32gb ecc stick in my system right now, with the same motherboard and a 5930k. I would try out the 64gb sticks for lulz, but they start at around...
Check your c-state power settings. I upgraded my bios to 3.10 and got a similar issue. I don't remember my exact setting, but if you disable c-states entirely you should be able to boot, at least, and tweak from there.
You might want to consider working on the board outside of your case...
I have done this and it does work, though I haven't tried it with multiple GPUs. My goal is to fit an air cooled gpu and a 10gbe card into an ncase, but I also have a Samsung 950, so now I'm trying to figure out how to do this bifurcation thing.