A really solid gaming build can be had for around $1500.
An i7 is used for programs that can fully utilize all the cores on the chip. Most games will use 2 cores, so an i5 with 4 cores would be plenty and save you a ton.
That Sabertooth board is WAY overpriced. You are paying a hefty premium for the look of it. It's not a bad board, but you can get one that does the same thing for $100 less. Sure, you would lose a couple SATA ports, but for a gaming build, who cares about that? Having said that, some people love the look and want to spend the money, looks are a personal preference thing.
A 750W PSU is way overkill unless you think you may want to CF down the road. For a single card like that, go with about a 600W PSU. You don't even need that much, but it never hurts to have a little extra.
For an SSD, I would stick with either Crucial or Mushkin.
As for the GPU, I feel the 680 isn't worth the price. If you look at the benchmarks, the 680 beats the 670 by maybe 5-8% and it costs $120 more. The performance/cost ratio just isn't right there. I would stick with the 670 and save the money.
As for Overclocking, I would get the unlocked chip. They don't cost that much more and you can always OC later when/if you feel comfortable doing it. It's quite easy and I always feel if you have the budget, why not have the option for such a small cost difference up front.
As for your build I would try something like this: