Motherboard model:
Rampage IV Black Edition

UEFI Version:
0801

CPU:
Intel i7 4930k

Memory kit part number (s) and amount in GB:
CMD64GX3M8A2133C9 48GB

GPU:
EVGA GTX 970 SSC

SSD/HDDs/Optical drives:

• KINGSTON SV300S37A120G
  
• ST240HM000-1G5152
  
• Hitachi HDS721010CLA332
  
• WDC WD2500BEVS-60UST0
  

PSU:
Corsair HX750

Operating system:
Windows 10

System Overclocked (provide details)?

• CPU multiplier: 45
  
• VCore: 1.35v
  
• XMP Profile #1: 2133MHz, 9-11-11-31, 1.65v
  
• CPU Current Capability: 170%
  
• CPU temp w/AIDA64: 68 celcius @ 2 hours
  

Issue

I bought a Rampage IV Black Edition mobo a little over a year ago off Amazon. My computer's been randomly restarting for the last few weeks; more often when I have a flash video playing, game open, or I'm trying to run some type of benchmark. No errors anywhere, no BSOD, just a sudden restart mostly at random times.
It would restart always during the following:

• Direct3D 9 ALU Assessment in Windows 7's experience index test.
  
• 3D Graphics DirectX11 test in PassMark's PerformanceTest.
  
• Memory Threaded test in PassMark's PerformanceTest.
  

Things I've tried that haven't worked:

• Default BIOS settings
  
• No overclocking
  
• Above overclock settings
  
• Updated BIOS
  
• New graphics card (Tested on GTX 660, GTX 750, and GTX 970)
  
• Reseated CPU
  
• Reinstalled flash
  
• Reinstalled graphics drivers
  
• Reinstalled Windows (from 7 to 10)
  

Not sure what else I can do to locate the source of this problem.
When reading up on the crash during the Windows Exeperience test, a lot of people had success with replacing the PSU.
When reading up on random restarts with the Rampage IV Black Edition, a lot of people had success with RMA'ing their board.
Doubt Amazon would let me RMA the board after a year. Thoughts on any way to definitely determine what's causing the restarts?

Edit: Also, not sure if it helps, but my mobo takes ~30 seconds to post. Seems really slow.