GTX 970 Overclock Crashes Whole System

[Proxish]

Hey, thanks in advance for reading and trying to help.

I'm no novice at overclocking, I'm just trying to confirm what I believe to be a faulty PSU.
When my EVGA GTX 970 SC ACX 2.0 is overclocked to: Default Voltage +110% +90 +120, running the Heaven Benchmark will crash my whole system within 5 minutes, cause a restart with no display, require a hard shutdown and then power up with a 40 second boot, opposed to the normal 20 second-ish boot.

Stock runs fine, Heaven Benchmark for 20 minutes had no issues.
Running overclocked crashed in 5:08.

I would of cut this down to just a bad overclocker, but as far as I know, a GPU overclock shouldn't crash a system, it should crash the program in question.
Also, I've had two previous GPU's in this build, a Gigabyte GTX 970 Windforce about 9 months ago, and more recently a Sapphire R9 290 Tri-X. Both overclocked like absolute garbage.
I unfortunately learned how poor the CX600M is a few months after purchasing it, a year and a half later, I'm assuming it's starting to die, if a simple overclock is going to crash the whole system, am I right, or do you have any ideas of what I can test?

So far:
Stock CPU Prime95 for an hour = OK
4.3GHz CPU Prime95 for an hour = OK
MemTest for half an hour = OK
Stock GPU Heaven 20 minutes = OK

GPU Info:
EVGA GTX 970 SC ACX 2.0
ASIC 74.8%
Memory Type: Elpida
Bios Version: 80.04.36.00.70

Again, thanks in advance for any help.

 

[sizzling]

A stable power supply is essential for overclocking, without it you will encounter stability problems. You really need a better quality PSU before thinking about OC'ing

 

[Proxish]

A stable power supply is essential for overclocking, without it you will encounter stability problems. You really need a better quality PSU before thinking about OC'ing

So you think the PSU just isn't good enough, and isn't dying?

I had an overclock of 4.4GHz on the CPU for a year and a half, and a small overclock on both previous GPU's without issue.
I've recently had to reduce the CPU overclock to 4.3GHz to get it stable again. And now a small overclock on the GPU is causing a total system shutdown and restart.