I got my Sapphire 5850 Toxic 1GB clocked 950/300 and that's pushing 363MHash/s and never goes above 60C (60% fan).
Even though it said that it couldn't adjust voltages I pushed it up slightly to 1.15 so the card became stable above 925 core.
If it couldn't adjust voltages, then how did you push it up to 1.15??
I am interested in that as well. When i try to change the Voltage Settings with RBE, it says there is only one fixed Voltage, 1,088 V.