Check out my $1100 build here:http://www.squidoo.com/electronicandmore#module147312351
Quite honestly, I don't think the 670 or Nvidia cards in general right now are very good cards at all. Personally for running those games the 7970 would be a much better pick. Especially since it costs about the same. You want the best for your money? The 7970 is the one to pick.
Clock for clock 7970: http://www.tomshardware.com/reviews/toxic-hd-7970-eyefinity-6gb,3264-3.html
Even a slight boost to 1GHZ the 7970 easily beats out the GTX 680 (Better than the 670) and that's not even changing voltages. Keep in mine the GTX 680 was clocked at 1006mhz.
7970 OC vs GTX 670 OC vs GTX 680 OChttp://www.hardocp.com/article/2012/05/14/geforce_680_670_vs_radeon_7970_7950_gaming_perf/3
The 7970 is cheaper than the 680, again we see it beat out the 680. The 670 is close in some but mostly beat out by a margin by the 7970.