Thanks Jovec.
The video card is not OC/overvolt, just running stock. The temps were fine according to evga percision, I never checked on the msi.
I stressed it with P95 when I first overclocked it and it went fine.
Would a 2GB card be fine at 1080?
Is there anyway to test the psu or pci slot other than putting another card in it and waiting?
Mild CPU OC, no GPU oc, two video cards dying in the same system - it's most likely the power supply.
2GB VRAM for 1080 is enough for most everything. CPU's OC can degrade over time for numerous reasons. When troubleshooting I would run the CPU at stock. 4.2 isn't a heavy OC for Sandy, but you will run to run p95 for at least 8 hours and also run one of IBT/Linx/Linpack for 20 passes or so to see if it passes both.
Regarding temperatures, you are monitoring your CPU and GPU temps during load?
If it is a power supply issue, it seems to be one causing issues over time, and I know of no way easy to test for this. You would need to monitor the 12v rail and connectors under load to ensure stable voltage delivery (consumer grade equipment isn't really accurate enough for this).
You could also move your failing/failed GPU into another system to see if it exhibits the same behavior. If it doesn't work it, your PS could still be the issue (as in, you PS killed the card). Either way, everything in your computer is effected by the power supply. You can get a quality unit in the 500-600w range for $60-$80 (enough for single GPU systems). I wouldn't buy a new GPU unless I bought a new PS.
Before spending any money, I would remove the heatsink/fan/shroud from the 560 and thoroughly clean out any dust. Clean the heatsink and GPU of whatever TIM they used (they usually use too much and use low quality stuff anyway). Use whatever CPU TIM you have instead and reattach the GPU heatsink. Depending on your GPU model removing the the heatsink can be easy or difficult so you may want to Google first. I easily got a 10c drop on my new 7950 GPU by replacing the stock TIM. Obviously this is only for heat-related issues and not PS/power delivery.