I found I could not overclock the XFX 7870 Core. Just running MSI Kombuster Burnin test on stock clock causes the GPU to hit 103C, and then it drops to 400MHz until it cools down. The card runs way too hot to overclock at all. In most games, it runs 85-95C. I'm honestly very disappointed in this card.
On top of that, the design of the card is very poor. My old 6850 blew hot air out the back, but the 7870 blows it all into the case. I'm not impressed by this XFX card.