Using 5870 for my main mining and it hovers around 250-300 m/hash
That's not efficient. My 5870 mines at 470Mhash/s right now, and it can probably do more but I don't want to push it too hard. Using 1030 MHz core, 300 MHz memory, stock voltage. Temps 60 degrees using a big aftermarket cooler (Accelero TwinTurbo Pro).