Something that fixed my crashes on a system I was renovating was running BurnInTest from Passmark.
Using it, I discovered that the CPU was overheating due to a problem with the cooling system.
Fixed the cooling system and the system is now stable.

Just shotgunning, but another thing to try is disabling the Efficiency cores in the CPU.
One less thing to cause problems, and you don't probably need them.

And I'm assuming that with a rig like that you're running at least a kilowatt PSU.