The specs for your case say it doesn't come with a intake(front) fan.Do you have a fan in the front?
If your XFX 6870's are the reference design then the high temps are normal.Reference cards have horrible heatsinks.I suggest adding a fan in the front if you don't have one already and add another fan or 2 to the top for exhaust.Better airflow should bring the temp down a little.
Reference looks like thishttp://www.newegg.com/Product/Product.aspx?Item=N82E16814150506
EDIT: I just looked again at the specs for your case and the pre-installed fans aren't that great.They run at 42cfm which doesn't move a lot of air at all..I suggest you populate all of your fan slots with new fans.That should dramaticly reduce the temps for both 6870's.
I suggest some of these fans...http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007998%20600035590%20600035654&IsNodeId=1&bop=And&Order=RATING&PageSize=20