This is probably the best build for the price, it would handle every game you throw at it without any problem at all. It could even play the games at 1440p at playable frame rates without problem at all. So this is the build you should go for. Also the CPU is overclockable, so you can extract quite a lot more performance out of it. So all in all this is a very good build for 1500 dollars. You should definitely go for it.
Also, there is no point in doing crossfire as AMD's Crossfire technology has quite a lot of problems and hence SLI is always preffered over the Crossfire and a single 780 is a beast and 95 percent of the gamers won't need anything more than a 780. And in the future you can just pick up another 780 and SLI them togerhter for much better performance. That is why i went for the single 780.