I believe my PC is dying

Hello all, just trying to get some feedback before I spend much more money. I have a decent gaming rig for several years now (Windows 10 Pro, i5-3570k, 16 gb ram and now a gtx 970 (got one 2nd hand from a friend over a year ago) and had no problems until recently. I had an SSD running the OS and a 2 TB hybrid drive for games and other programs. Just before Christmas the system started slowing down and in particular anything on my secondary drive started taking a long time to do anything. I figured the drive might be dying and used an older drive that I cleaned and formatted to replace it and everything seemed fine when I left town to visit family. After the new year I was back in town and the rig was fine. Work started a few days after that and then the system died. Came home and brought the system out of sleep via spacebar and nothing happened. Computer had power, but neither monitor changed from black, even after cycling power on them. Fans were running, but no activity on hdd light. I left the system overnight (it was already quite late and I had work in the morning) and there was no change so I risked a reset. At that point my SSD drive with the OS was not detected by bios at all although it was detecting the secondary drive. Swapping cables did nothing, the SSD remains dark

So I figured that was that, the SSD died on me. I bought a new one and had it shipped to me. I was able to borrow a laptop and get a usb windows install. I was able to install windows to both the new SSD and later the secondary HDD (to see if the new SSD was bad), but new problems sprang up all over. I was able to update via windows update, but while quick scan worked, full scan on windows defender always hangs and stops at some point. Installing new gpu drivers via GeForce Experience and direct download fail almost everytime (I this point I have formatted and reinstalled windows multiple times) and even if get them in, the two games I installed (Prey and World of Warships) both crash as does a benchmark for FFXIV that I downloaded. I had several bluescreens of death, the one I caught said Clock Watchdog Timeout for the error. I'm fairly stumped at this point. MemTest 86 came up fine as did the intell CPU test program. However Event viewer is showing multiple instances of

Reported by component: Processor Core
Error Source: Corrected Machine Check
Error Type: Internal parity error
Processor APIC I[​IMG] 0

And the system has crashed/restarted several times. Given the tests above, I was thinking the GPU might be failing, but honestly I have no idea at this point. Anyone think of something that will cover those bases or is it time to just do a complete rebuild from the ground up.