Your AMD requites 2 6 pin connectors. the 770 will need 1 6 Pin and 1 8 Pin so make sure your PSU can handle it. Also what PSU do you have? Should be just fine if your running a 6870. Just when you upgrade what i would do is uninstall ALL AMD drivers first. Then restart and make sure they are still gone. Then shut it down, replace video card, then go to nvidia and download the lastes 331 WHQL drivers and should be good to go