Trying to get mobo to POST with Q code A9 and 99, no display. Possibly GPU?

Hi all, this is my build:


PCPartPicker part list: http://pcpartpicker.com/list/3Vm6sJ
Price breakdown by merchant: http://pcpartpicker.com/list/3Vm6sJ/by_merchant/

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($344.99 @ SuperBiiz)
CPU Cooler: Corsair H115i 104.7 CFM Liquid CPU Cooler ($99.99 @ Newegg)
Motherboard: Asus MAXIMUS VIII HERO ATX LGA1151 Motherboard ($199.99 @ SuperBiiz)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2400 Memory ($64.99 @ Newegg)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2400 Memory ($64.99 @ Newegg)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive ($160.58 @ Newegg)
Video Card: EVGA GeForce GTX 1080 8GB FTW Gaming ACX 3.0 Video Card (2-Way SLI)
Video Card: EVGA GeForce GTX 1080 8GB FTW Gaming ACX 3.0 Video Card (2-Way SLI)
Case: NZXT Phantom 530 (Black) ATX Full Tower Case ($119.99 @ Newegg)
Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($117.98 @ Newegg)
Monitor: Asus PG279Q ROG Swift 27.0" 165Hz Monitor ($749.00 @ B&H)
Total: $1922.50


I'm having trouble getting the mobo to POST with the graphics cards connected. When I try to boot with:

- Both GPUs: Q code 99 (Super IO initialization), no display, GPU fans start and stop

- GPU 1 only: Q code 99 (Super IO initialization), no display, GPU fans start and stop

- GPU 2 only: Q code A9 (Start of setup) occasionally, other times Q code 99, no display, GPU fans start and stop

- No GPU: Q code 99, BIOS displays (I suspect the Q code is because I'm using liquid cooling and it doesn't detect a CPU fan in the mobo)

All boots run through several Q codes (25, 41, 35,62, and others, before settling on 99 or A9)
When I get the BIOS to display I get a CPU fan error. However, all my RAM, my SSD, optical drive, and the HDD I moved from my old build appears.

I've been using the 2 6+2 VGA power cables to the aux power of the GPUs rather than the 6+6 adapters the GPUs came with (since I wouldn't have enough cables otherwise), in case that affects anything.

So I'm looking for what exactly this means. I have my own suspicions, but this is my second build so I'm hardly an expert. What do you guys think?


UPDATE:

I moved the cooler's 3 pin from the fan hub in the back of the case to the mobo's CPU fan header. Now the Q code with no GPUs is A0, and it boots to BIOS. Tried to install windows (to see if I can maybe update GPU drivers?) and it's giving me the "A required CD/DVD device driver is missing" USB install bug.

UPDATE 2

Ok, so I ran several test cases, so here are the results

Any single GPU, in either PCI-E slot: Everything powers on, Q code 99, there is an audible click, GPU fans turn off (lights on), bios loads, Q code changes into AE, then A0. However, GPU fans will not turn back on unless hard reset. Reset button on mobo doesn't turn them back on.

Both GPUs SLIed: Same as above, except nothing displays on the monitor regardless of where I plug it in (either GPU, mobo)