I have 2 Vapor-X in my rig and they are great. I run them at 950 MHz @ 943 core voltage. They pull just 172 watts out of the wall. In litecoin mining I get 560 kH/s. From an efficiency point of view not a bad ratio.
Is that 560 kH/s each or both? My single 6870 is pushing 320 kH/s with zero errors @ 850 MHz intensity 15. Not sure the watts