Hello, I have exactly the same situation and problem, just small changes in components of my computer, but it is almost the same, Asrock motherboard, power supply 650w, before I had GTX 550 ti and bla-bla-bla. And my videocard is Gigabyte GTX 970 Winforce 3x right now.
When I start my computer everything is working including the videocard, but I can not see anything on the screen, when i put out my videocard, integrated videocard is working. So, exact the same thing happen to me.
You posted this topic on December 3rd, so I think you fixed this problem already, can you help me ?
Thanks,
Anton.