S!
Well..as my 7970HD has the dual-BIOS I decided to bite the bullet and update my card with the GHZ Edition BIOS. This boosts the frequencies from stock 925/1375MHz to 1050/1500MHz and adds a boost feature etc. So far so good

CoD runs fine and card did not go over 71'C
Now I should get a bigger PSU and try OC the i7 3770K slightly. I have a Thermaltake Frio cooler on it so maybe it should handle around 4Ghz from stock 3.4GHz...