alot depends on your case you have to consider airflow. amd cards run cooler then nvidia and the dual gpu's under stress need plenty of airflow. also todays cards are big make sure you measure before you buy. you should research because if your gonna play wow or sims games like that you dont have to go balls to wall! if your playing bf3 and mw3 go with two 670's in sli more then enough to run anything out there....if you can keep them cool.