New system won't POST, spent a good two hours trying to figure out why

So I recently built my own computer (second build, first build was for someone else), and after putting everything together and plugging everything in, I press the power button, all the fans turn on, the optical drive turns on, the LEDs on the motherboard turn on, but the computer won't POST.

I have done everything I can to troubleshoot without taking everything back apart.

-made sure everything was plugged in correctly

-made sure the RAM and GPU were pushed all the way in

-made sure no wires were running underneath the motherboard

And a few other things, so I'm just about ready to take it all back apart and try and do a breadboard, as well as see if the standoffs are installed correctly.

Which brings me to my question.

The CPU power connector on my PSU is for 8 pins, but it is split into 2 seperate 4-pin plugs. One of the plugs does not seem to match the pins it should connect to on the mobo (which needs an 8 pin plug). I'm suspicious that this may be part of the problem, so I was just wondering if anyone has encountered this sort of thing before? I'm sorry if I did a poor job explaining it, if you need me to elaborate just let me know. I would appreciate any kind of feedback before I basically start this whole build over again. Thanks!

-Intel i5 3570k cpu

-ASRock z77 extreme 4 mobo

-CORSAIR Enthusiast Series TX650 V2 650W ATX12V v2.31 PSU

-Corsair XMS3 8GB (2 x 4GB) DDR3-1600 Memory

-EVGA GeForce GTX 670 2GB Video Card