Hardware advice on a new build

Hi all,

Been doing some research and starting to select my build, would greatly appreciate some advice! 

The GPU's are the only thing I haven't picked yet, of which I'm going to get 4x
I'm about ready to accept i'm not going to find any 1080 Ti FE's or even 1070's for that matter. 

So really my question is, how bad of an idea is it to place 4x 1080 Ti's next to each other? If that's your only choice what extra steps would you take to protect them?

ASUS Turbo GeForce® GTX 1080 Ti 11GB GDDR5X is my lead contender so far.


For the rest, i'm equally open to any advice; please let me know your thoughts:

Mobo: Asus X99-E WS Socket 2011-v3 CEB Motherboard

CPU: Intel Core i7 6850K Extreme (Broadwell-E) Socket LGA2011-V3 Processor

CPU Cooler: be quiet! BK019 Dark Rock Pro 3 CPU Cooler with Dual Silent Wings Fan

Memory: Kingston HyperX Fury Black 64GB (4x16GB) DDR4 PC4-19200 2400MHz Quad Channel Kit

Case: Corsair Obsidian Series 750D High Airflow Edition Full Tower Case

PSU: EVGA SuperNOVA 1600 P2 ATX Power Supply

SSD: Samsung 850 Evo Basic 500GB Solid State Hard Drive 2.5"

Thanks in advance!