Usually, the newer card is always better than the older card. But, you say that you are looking at a 680m SLI laptop. That will be faster than a single 780m no matter what. From what has been leaked about the 780m, which very little [just a benchmark score with a new Haswell CPU] the difference between one 680m and one 780m is a mere 10-15%. A cuurent Ivy Bridge with 680m SLI will own a Haswell with one 780m. If you wait a few months until these new platforms are released, that 680m SLI system might be marked down a bit, since they will want to get rid of all the "old tech" to make way in their inventory for the new stuff. If you can get the 680m system for less than the 780m system, get the 680m. If they are still the same price when the 780m SLI+Haswell comes out, get the new system.