What is your overall budget? What you already have (peripherals, reusing any parts)?
CPU- 4790 is great but the 4770 will save you money and perform just as well. Get the unlocked version if running a tab below the 4790 would leave your butthurt.
Mobo- Asrock's boards are pretty killer and usually sell for less than Asus or Gigabyte. Don't get me wrong, I like both of them but less for equal or better just makes sense.
RAM- I guess I am a touch old school but I stick with G.Skill and have since s939 days (Google it). 16GB is great but you can run with 8GB and never notice the differnce.
OS drive- definitely go with an SSD. 120 would be the minimum for the OS drive. I am running a 120 SSD myself and have about 55GB open so that'll work.
Hard drive- serious advice here, get another SSD for your games and a mechanical for storage. Go with either a 256/240GB or (preferably) a 512/500GB SSD. Grab a WD Black mechanical of whatever size you think you will need for storage (video, music, whatever)
Case- personal preference
GPU- the 960 is a good choice