Sorry sinthoras, IMHO there's no such thing as overkill
So , lets throw all our money away just because we have a lot ?
What else can you call this situation ? If he wants to use 1 monitor and goes for SLI. What is this if not an "overkill".
I hope you wont say "futureproof". There is no such thing. You will never catch up technology development , there will always be newer stuff.
You simply buy the best bang for your personal buck at your time and when you need to upgrade your rig in the future you simply buy the future's best bang for buck.
It wont be wrong to think like this ; One of the 680s will simply stay inside his case and do nothing in his 1 monitor setup. It'll slowly get outdated without being used even once inside the case. This is just a figure of speech and example , I do not claim this is an absolute fact. But this is gonna be what the situation will look like.
x79 is a waste for gaming. The price/performance is terrible over the i5 2500k. 2x 680 is wasted money on 1980x1080p. I'd drop 1 680 and the x79 and get 2 more monitors. 1x 680 is pretty good at 5790x1080. Then when you grab 2 you can pretty much max anything on 5790x1080p until you hit the vram limit. When the 4gb versions come out then you'll see the 680 trump the 7970 even harder.
i'm waiting for the 4gb GTX680 anyway.. i think i'll buy 2 extra monitors within 6 months after system purchase.. and i most certainly want to max out every game on any resolution.. maxed out below 60fps makes me cry