If you don't overclock then there is no reason to go with the K version of the CPU. I have ran WD blacks for years with no problems, i like the extra speed when i am moving files back and forth off my SD drive, but they are louder then most drives so if noise is a concern stay away.
If your going for such a high end build get the K regardless, it's a minimal price difference that you may eventually use or at worst it will keep the second-hand price much higher / more likely to sell.
I also agree with getting a k version cpu, is a waist not doing so, mem g.skill is the best ram in my opinion. PS stay 750 or up for the headroom and a major brand as u have been suggesting all through your posts.
I run the newest gigabyte board been on asus for years needed a change, I like it. Asrock I have used but only the one, didn't use it long before changing to asus so.
Sound believe a sound card should be in order, I know allot of the onboards are good these days but there just that, onboard, a good asus sound card you should have a look at.
Have a freind that just bought a new build and went with a 680 turned out he was getting crashes on certain older games and ended up buying a 7970 to replace it. Just something to think about.
Again u mentioned gaming so a 120 hz monitor you should also be looking at, use a 27" now is 3d though have never used it. use an ati card so too don't play nice together for 3d, gaming normal is fine.
Don't be confused when we have conflicting advice! Each one of us has his/her philosophy when it comes to PC building.
If you overclock your i7 CPU and HD 7970 GPU card to the maximum with 4 fans, 1HDD, 1 SSD, fan controller, SD card reader and sound card, you're rig will reach 480W power consumption. Your maximum at stock would be around 430W and average at 400. If you have money to spare, then going for something higher than 650 on a good quality PSU will allow it to operate fanless or at a lower fan speed. It will also allow you to add another card down the line should you wish to. So I think it's a good idea if:
1) You can afford it after getting the best (other) parts you can get first.
2) You are going for a quite PC build
3) You intend to upgrade.
For GPU, I don't think the GTX 680, with its current price/performance makes any sense since the HD 7970 can match it and is $50 cheaper.
Matrix is an awesome card (if you can find it) and it has the highest clocks, but way too expensive and huge (triple slot cooler).
All manufacturers charge $50 extra just for overclocking their cards to take advantage of novice builders so I would get the best dual slot design for the best price and try to overclock.
MSI TFIV are also expensive so my choice would be $400 Gigabyte HD 7970.
PS: If you are going for a sound card ( any Asus Xonar AV100 chip equipped soundcard), then an Asus motherboard is due imo.