your temps will drop like a rock if you get that voltage to the proper level.. typically i have it at 0.05v above my mhz level. its WAY better for your cards, you'll reduce how fast you heat up the room and it'll be quieter with the fans slowing down some

for example: 1.0ghz = 1050 (1.05) voltage in afterburner


also.. the 7970 is about 5-8% faster mining vs a good 7950.. but 33% more money (400 vs 300 usd in the states)