At normal ambient temps, about 20c, I can run mine at 2150 game stable, and it stays there. Those clocks I referred to before are benchmark stable.
Core temps are everything...the lower the better. I would shoot for no higher than 40c on the core to be able to retain a decent clock without having to touch the voltage. I can maintain that 2150 for gaming, without adding any additional voltage (it runs 1.043v at that clock / temp), without ever going above 40c (ambient temp of around 18-20c)....and, as I said before, this card isn't a great overclocker.