I have tested all kinds of configurations and finally the highest hashrate I can get out of my 7950 cards (with stability) is 630 KH/s. I have seen people reporting hashrates of over 700KH but I just can't imagine how to get there at this point.

Currently the cards are configured as follows:
Intensity: 20
Powertune: 18
Memory freq: 1575
Engine freq: 1110
VDDC: 1.1 V

With these parameters I have the cards running stable at around 72°C. If I increase the engine frequency I might get a few more KH (not so many) but eventually the whole system hangs up or one of the cards appears as "DEAD" on cgminer. I have also tested a very wide range of different frequencies for memory and GPU engine but this is the best hashrate I have achieved.