Are you interested in over-volting? If so, you need the lightning or classified 780 cards. Keep in mind over-volting has a price to pay in terms of noise and heat output. The ACX cooler (used on the classy) is very good, but not as good as the DC II or Windforce 3 rev. B. Going on, you will likely get the highest OCs with the classified, but the classy costs 580$ minimum. The Windforce and DC2 cards are excellent overclockers as well and cost 510$ and 520$ respectively. IMHO, unless you really want to over-volt (with the understanding of the caveats above) I would get one of the latter two - my personal preference is the Asus DC2, but i'm admittedly an asus fanboy. They are both excellent cards. The classified is excellent as well but does cost a good chunk more.
You also have the option for the 780 SC ACX - it will not OC as well as the classifed and the ACX cooler is not quiet as good as the windforce or the DC 2 - but it's still very very good and quiet. It should boost past 1000 out of the box very easily, as mine does.
Basically you can't go wrong with any choice. If you want to over-volt, though, you need the classified (580 or 699$ depending on where you get it) or the lightning (540$) - keep in mind the caveats with respect to heat and noise, because over-volting gives you high clockspeeds but there is a price to pay. I used the 680 lightning which OC'ed past 1400 but it definitely was NOT quiet at that speed. At normal speeds it was quiet - I could OC to ~1250-1300 no problems no noise. But overvolting a lot made noise a problem - this will apply to the classified and 780 lightning as well i'd imagine. To overvolt the lightning you need to email MSI for a special edition of afterburner. To overvolt the classified you simply download the classified voltage controller.