Either 1600 or 1866 MHz will do for gaming. Unless doing benching there isn't any visible difference between them and going higher. The 3570k is stated to work with 1600, if it doesn't you are able to rma it. Over 1600 the Ram is overclocked and you have no Insurance if the cpu where to be unable to handle it, though you need around 2400 mhz and then it is a slight chance. The Formula supports up to 2800 mhz memory.
Save yourself some money and get a 1600/1866 mhz 2x8 kit.
I have no comment on the rest of the build. It's well thought.
| Chassi: Phantom Fulltower White Edition | Mobo: Maximus V Extreme | CPU: i7 3770k
| Memory: 2x8gb G.Skill Trident X 2400mhz | GPU: PNY Geforce GTX 670 | PSU: NZXT Hale 90 750w
| SSD: Intel 120gb 330 series (OS) | Intel 120gb 330 series (Games n stuff)
| Monitor: LG 29EA93 | Cooling: Custom Loop