I won't have to fiddle with OC (I don't trust myself with that).
Eh, as before overclocking is pretty damn safe these days so long as you don't bother increasing voltages, pretty much every card can hit the same speed as any factory overclocked card on on the market. For example, any HD7970 can hit the 1050Mhz Core/6Ghz VRam speed of the HE7970Ghz and can even go faster then that without touching the voltages, the reason they don't at stock is because of noise since the cooler can handle the heat, just not without making it run loud enough that people would complain about the noise.
The few outliers in that would be certain custom types like the models that come with a preinstalled liquid cooler or something like the MSI Lightning series, though that's also got tons of marketing hype about how many extra voltage regulation rails and whatnot they added that are just beyond overkill and add no actual benefit unless you're going for cryogenic level temperatures for competition class overclocking.
Thus any 680 should be able to hit around the 1.2GhzCore/6.*Ghz VRam of the factory overclocked cards.