I would go with the two 780s as far as the graphics cards if your're looking for really great performance and the 850w should be plenty for what you've got ( I have the RM 750 its awesome). As far as the motherboard that sniper isn't going to work because they don't make a sniper board on the 2011 socket. You're using a 4820k so you need to make sure you're using a socket 2011 board for it(preferably a higher end board because you're using a ivy bridge-e chip I would recommend an Asus Rampage IV mobo if you're looking for really high end gaming. I have an H100i and you're defiantly going to want to replace the stock fans because they're really loud I recommend the Noctua NF-P12 1300. Everything else looks fine but I've heard a lot of mixed reviews over barracuda drives and would recommend a WD Black if you like higher end HDDs I have one and I love it. When you're installing your OS just keep in mind that the H440 doesn't support 5 1/4" drives so you'll have to install off a flash drive or external disc drive. I just have one question about all this which is why are you going for such overkill? If you're just doing standard gaming (also may I ask what resolution you're monitor(s) is for all this?) then this is way over the top and I could recommend some different options that won't hit the wallet so hard.
To be honest who doesn't like overkill ;D! Thanks for the advice! I'm thinking of running a 34-inch LG ultrawide (3440 x 1440) along with a 21 inch 1920 x 1080.
Here is the motherboard I think it perfectly compatible, I went over it again and I didn't see anything wrong.
No, don't use the 4820k unless you are thinking about upgrading later on to the 4930k, because that only slightly better than the 4770k and it isn't worth the extra money. Also, you can just go with the 4930k because that is a nice chip and is actually worth the money you pay for it.
I suggest getting the 6 core i7 if you go with the 2011 platform. The i7-4820k is very comparable to the i7-4770k on the cheaper 1150 platform, and isn't really worth the price premium.
Dual GTX 780s will be good for gaming. However, for productivity rendering and stuff like that, you can usually only optimally use one GPU. SLI is only for gaming. Since your build is gaming centric, dual GTX 780s are a good pick. A single GTX 780 should be plenty for light graphics editing.
I would go with a 4770k really that will be perfect and I just looked at thay mobo and no seriously you can't use that one. That motherboard supports socket 1150 the cpu you're using is socket 2011 so it won't work together. If you use a 4770k it'll work but the cpu you want isnt compatable
This is a total build I would recommend. Like others said before, the 4770k is the best option for gaming because you can put the extra money into higher quality components for overclocking, better storage for efficiency and backup, and better case for cooling (while keeping it quiet.)
Post your max budget so we can help you out further, this is what I would be looking at:
http://pcpartpicker.com/p/3Bbru
There is nothing really too excess, but everything is premium quality.
The storage is 128gb SSD for OS, 250gb SSD for games, and the HDD for long term backup and media. The noctua cooler is only a LITTLE warmer than an H100, but a hell of a lot quieter. Its silent.. as are the noctua case fans.
Here is a cheaper, but still good quality build: http://pcpartpicker.com/p/3BcB3
This has less ram (8gb), but its all you need for gaming, and the ram is slower, but the performance increase for faster ram is very minimal also. The other differences are just cheaper, but still high quality options. You can still get a good overclock on the asrock extreme4 and it has a good layout and quality parts.
There we go. I just removed the case fans. The included case fans are already reasonably quiet. That will be a killer machine man. It will be difficult to do better than that.