Just switched to CGminer from Guiminer/poclbm and for those who have the issue where Guiminer decides to power off your card and start producing really low hashrates well by switching to CGminer this is not a problem.

If anyone is interested this is my machine:

Antec 900w HighGamer PSU thingy
AMD Phenom II 1100T BE
Gigabyte 990FXA-UD5
Corsair C9 1600 Vengence Ram - 8GB
Powercolor 6990
Asus DirectCUII 7850
Gigabyte 7770OC - This card is so power efficient im thinking of doing a 6card low power rig with these.

Maxes out around 1.2GH/S under CGminer and is so much more consistent in hash rate.

The 6990 under Guiminer would occasionally get 370mh/s per core but under CGminer its fairly consistent now.