The 1200W power supply is unnecessary, you only need a 650W at most for that system. A 750W PSU will give you enough headroom to add another GTX 680 later on for SLI. The Corsair AX750 is a good 750WPSU if you want the Gold efficiency and is also fully modular.
As far as the graphics card goes, personally I only ever buy reference design cards as they tend to be more reliable. The Asus DirectCU cooler is supposedly pretty good, but the GTX 680 runs cool anyway for a high performance card. If the slightly better cooler is worth $100 to you, then fair enough.
Personally I'm not a fan of Corsair Vengeance memory, when it first came out I found it very unreliable. If I remember rightly I went with 32GB of RAM for the system I originally specced up for you, mainly because that's what you had originally chosen. At the very least I would go for a 2x8GB kit rather than a 4x4GB kit, as that will leave you 2 slots free for further expansion if you don't want to get 32GB right away. Memory speed is irrelevant as it provides no performance increase, so don't be fooled by the higher numbers. One thing I did make a mistake on - you will need Windows 7 Pro or Ultimate to use over 16GB of memory, Home premium will not address anything over that amount. You'vealready addressed that so that's cool.
The Corsair H100 is pretty noisy and only as effective as a top end air cooler. The Noctua NH-D14 is cheaper, quieter and cools just as well - it does need a big case but it doesn't require 2x120mm fan spaces as the H100 does. I am really not a fan of the all-in-one liquid coolers as they're just more expensive and louder than a good air cooler.
As for a case, that's partly a personal decision, depends what you want it to look like. I'm a fan of the Bitfenix Shinobi and Shinobi XL, the Fractal Define XL, Corsair 600T, Coolermaster HAF 932 and HAF X, Silverstone Fortress FT02, or maybe take a look at some of the Lian Lis - they're expensive but very high quality. The PC-P50, PC-Z60, K-62, PC-90, A-71and B-25 are all good cases.