Hmmm, I know you said you replaced the PSU, but I can't help but think that's the cause since your setup works with the stock video. Maybe a bad batch where you got them? Hope you fix it so you can start playing!
Glad it worked out. In another life I did numerous windows updates on too many pc's to count. In case someone else has a similar issue here is a quick process that usually works to "un-stick" updates. In fact I had to do it on Windows 8.1 a few days...
Hey! dropping in to say hi. Been playing with computers for along time in fact my first pc had 16k Ram and one of the first games I recall was called Colossal Cave. Anyway just got an Asus hero vii, 4970k, and some other stuff to update my home syste...