Issues with Z97 Extreme6

This is my very first build and I've had a few issues that I'm unsure how to fix.. I was thinking it might possibly be a faulty motherboard but i want to be absolutely sure before i decide to RMA.. i Took it into a shop to see if they could diagnose the issue and it was an absolute waste of 80$.. so onto the issues.. The picture quality has been atrocious to say the least when i watch videos whenever there is a dark scene it gets very pixelated and almost has a green tint to it.. Text has a rainbow color to it some letters will look blue some purple.. I can see static like from an old tv in the background as well.. games Weren't preforming well either i was getting slow down and some pixels which i did not get in my old pc with the exact same games.. I thought it might be my gpu so i tested it in a different pc and it worked just fine.. also tested out different monitors and all had the same issues on this pc.. No one has been able to help me and I'm at my wits end.. any help would be appreciated and thanks in advance.

I tried both pcie slots and even took the card out and tried the onboard graphics.. still the same issue 

racminer wrote: Hmmm very strange... Have you looked closely at you mobo connector, it is an HDMI I suppose?

is this the one ? http://www.asrock.com/mb/intel/z97%20extreme6/

I see that there are two connectors DVI-I and HDMI ... have you tried both?

I've tried both issue still persists.. the shop just got rid of drivers that were conflicting with each other and did fresh installs.. which wasn't the issue because it fixed nothing.. i was thinking maybe psu? but 850 should be plenty.