My sapphires are quite stable at 0.85v up to 780MHz. Helped the GPUs to not go above 75C at 60% fan speed. I can't get past 800MHz @ 0.95v though, had to use 1.0v for it to be stable up to 840MHz.
Wow, your temperatures seem extremely high to me.
I just remoted into the rig and this was it's current temp readings. 3x 5850 1x5830 all 825/150/1v
http://i49.tinypic.com/2u8a236.png