None of those games listed will get any benefit from an i7 , the top i5 would do the same job
and 4gb cards are overkill for all of those games
Even BF3 in triple monitor mode only uses around 2gb of graphics memory (set on ultra settings)
So your 2 GTX 680's are basically going to run the same as your GTX690 short of running cooler
I concur you won't see much of any improvement. Save your bucks and spend it all on your triple monitor setup, a lot of enthusiast gamers don't spend nearly enough money on their displays, the one thing they will probably keep the same for 2 to 4 upgrades.