How much is the 3TB wd red ? Because the barracuda is slightly faster, same reliability and cheaper.
I'd get a ssd, it will improve the loading of the games and maps, will boot the os faster, improves the system responsiveness.
With a 2000$ build more or less, a ssd should be included, you can just get 2TB hdd.
Also a quality psu with 750-850 will do for the system(with two 670 GTX).
The xfx is fine, it's a bit overkill, it was from the other list of a suggestion, but it's a high quality psu made by seasonic and modular.
If you want a 750W psu, i suggest the rosewill capstone 750M, it's made by super flower another high quality psu, it's as good as the corsair, but i bet it's a lot cheaper : http://www.newegg.com/Product/Product.aspx?Item=N82E16817182264
Review here : http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story5&reid=266
The new ax series seem to have a e high pitch noise or coil whine.