I own a 7990, and one problem I had with it is that the cooler would blow the hot air in the direction of its own intake, so when gaming (or mining when it was profitable) it would recycle its own hot air, and get to 90 degrees in gaming (mining with a closed case would be suicidal). My solution was ghetto mounting two fans from the rear of the case below the gpu, to give the card dedicated airflow. it still idles at 40-45c but it doesent go over 70 in gaming.
So make sure your gpu isnt reusing hot air.