apparently the 68XX are more effecient on power/hash than the 58XX series.
More efficient of power but less efficient in hashing so 58xx series = greater profit still.
5830 / 5850 is sweet spot. I have 4 more 5830s unopened waiting for a mobo and junk... and then I'll have 8 of them mining at about 2600 mhash
I have 2 5830s and im only getting 474 - 486 mhash in ubuntu no gui stock machine using sapphire extreme 5830s ...