What i wanted to say: Smaller cards are sufficiently using their vram.
A correction from my side concerning this: As cards are getting larger vram, multi gpu can be used without any limits, because every card has enough. Smaller cards in current sli state are less efficient, because they get bottlenecks and up to now and with current techniques, it will not change very soon.
That is why I always suggest not to upgrade with sli. Perhaps this changes, but i bet, that it will take several more years to take it into consideration without these doubts. I was not referring to your system, because you have too much reserves. U just can see, that it is not efficiently scaled and this is often the case.
Concerning sorround: New nvidias also have them ready for surround gaming, but sorry: I am also an nvidia guy normally, but when you talk about sorround gaming, eyefinity is the betterbsolution and ati cards are performing way better in high resolutions by nature. So, we have to wait for the real kepler
to evaluate their behaviour.
Up to now, the 680 dies against 7970 in high res or better say ultra hgj res with triple monitor setup.