I was a little concerned, in trying to improve your build, that I was going over budget, until I realised your original build was way over your stated budget, even more so if it was meant to include OS.
I've put together something, "similar" to the original, but cutting back, where sensible, at the same time, as giving improved performance. Possibly not what you were looking for, but a starting point, to help decide "which way" you want to go. PCPartPicker part list / Price breakdown by merchant / Benchmarks
Ahhh. That explains a lot, if you already have GPU, and that's not in budget. I started making a few minor changes, including a better, but CHEAPER GPU, and couldn't understand why I was going way over budget.
Taking that into account, revise, if you wish, as follows,
Motherboard: I used a cheap mobo, to cut costs. It's good value, but not as good quality as Asus. The one you chose, was designed for Sandybridge processors, whilst it will work with Ivybridge, a Z77 board will be better. If you want to go with Asus (good choice, got one, myself), the best mix of performance, and features, for gaming, is probably Asus P8Z77-V.
RAM: 8GB is more than enough, for any gaming. The only sort of stuff, that benefits, from more, is high-end photo/video editing, or perhaps 3D design. If you want 16GB, get 2x8GB, 1600MHz Low Profile, like Corsair CML, GSKill Ares, or Crucial Ballistix Sport. If you can get C8, or C9, great. If not C10 is OK and usually cheaper.
Video Card: The GTX660Ti is better than GTX570, but if you've already got it .....
PSU: That power supply is to allow for, eventually, TWO GTX66oTi's. As you've already got GTX570, PSU should be changed. If you have no intention of adding 2nd GPU, in future, use PC Power&Cooling Silencer MKlll 600w. If you want to allow for two graphics cards, you should go up to 850w (the 570 uses more power, than the 660Ti)
Case: Your original choice was much more than necessary, so I dropped to the 400R. That is plenty, and decent quality. Of course, if you particularly like your original choice, it is quite good, so, if you don't need to save money, go with your original choice.