I have Sapphire HD 7950 in my rig, and I wish to overclock it. I've tried before using MSI afterburner, but I've had problems when testing for stability. I've tried both MSI Kombuster and Furmark, but even when I put the core clock to 1250 MHz, I wasn't seeing any problems when running either. My temperatures stayed in the 60's C, which it did at stock anyways.
Basically, I have two questions:
1) How do I effectively test the card's stability?
2) Would it be worth it to change the voltage? (I have a 650W Corsair PSU and i5 3570k @ 4.5 GHz, power shouldn't be an issue)