The 68xx's are garbage for mining at the price point they are being sold at. They would need to be around 100-130 to be even considerable. Go with the 5850 sapphire for 176. People have said multiple times that the sapphire can go 408 on stock voltage.
I've read that too but doesn't the 6870 reference get more shaders through a bios mod or something that get it similar if not more than the 5850?