Save some money and get 1600 MHz ram. Get the first build. You won't need 4GB Vram on a single 1920x1080 monitor. If you play at a higher resolution go with the 4 GB.
What's your display setup?
I`m using single 3D 1920x1080p monitor. Thanks for reply!
There's things I like about both configurations, but the 'MSI GTX 680 Lightning 2GB' is a better OC GPU. I like 4GB GTX 680's but I'm also running 3xHD (3D Vision) where 2GB is an issue, but in 1xHD (1920x1080) 2GB vRAM is fine and it's fine for a 30" (2560x1600).
BTW - get at least a 1TB HDD (7200 RPM), 500GB is, if you're a gamer, way too small; 2TB is better.