I also highly recommend Kalroth's version of cgminer! The xIntensity feature allowed me use 2 threads with my 7950, getting it to hash on par with my 7970!
http://k-dev.net/cgminer/You're getting over 700KH/s from a 7950?

If this can be confirmed that'll be a mini-game changer for mining.
I'm getting 700 now from my sapphire 4L 7950s.

What temperature are your cards running at and what is the ambient temp? I'm thinking if it's not to bad, I should make the switch...