I would go with the GTX 770, my current card actually. It introduces technology GTX 680 doesn't count with such as Turbo Boost 2.0, etc.
GTX 770 have more advantage since it will deliver:
-Higher memory bandwidth 224 GB/s vs 192.3 GB/s
-Higher clock speed 1,046 MHz vs 1,006 MHz
-Higher effective memory clock speed 7,012 MHz vs 6,008 MHz
That leads to better performance, benchmarks/FPS