Computer doesn't turn on after after being shut down for a long time

[eba_devil]

So I recently built a computer, 5930K OCed to 4.0 GHz, ASRock X99 Extreme 6/ac, EVGA GTX 980 SC Edition x2, 4x 8GB Crucial Ballistics DDR4 RAM, Samsung 850 EVO 1TB, Samsung/Seagate M9T 2TB 5400 HDD... it's all powered by an EVGA 850W PSU

It's been about a month and a half that I've had the system but I had to RMA one of the video cards so almost this whole time the system was running with one VGA card... I got the card back Thursday and now it seems like the computer turns on ok if it's been recently on, but if it has been off for a while (like a day or so) the system seems to turn on but the video cards don't output a signal to the monitor... it was ok before the second card arrived... is it possible that it's insufficient power? Does a PSU even work like that? Could it be the video card's fault? Why would it turn on ok if it's been on recently but not after a long time off? Can the overclock do something to the system? I turned the CPU overclock off just now so clearly I won't be able to test it for a day or so (give it time to be "off")... but what are your guy's thoughts?

This is approximately all that's plugged into the system plus 4x 140mm fans and 3x 120mm fans
http://pcpartpicker.com/p/fkJMgs

Should I consider a larger PSU? What do I do with this one now? Do you think turning off the CPU overclock could solve the issue? Could it possibly be something else?

 

[eba_devil]

any thoughts guys? I power cycled the PC last night as well... will see how it does after I come how from work today... I was reading that it could also be a monitor issue? I bought my monitor refurb... any ideas if that might be what's happening here?

 

[ASRock_Support-2]

Hi,
I'm Davis from ASRock HQ TSD.

For this case, we provide few ways for you to verify and narrow the problem.
1.Please load BIOS default setting.
2.Please only install necessary devices(CPU, fan, VGA card, power, memory) for testing without OS and narrow problem.
3.Please only install one VGA card to check whether the symptom still exist.
4.Please only install the RMA VGA card for try.
5.If two VGA cards are passed your test, please change another SLI bridge for try.
6.If possible, please change another monitor or VGA card for verify.

Thanks a lot !!
ASRock TSD