Mike i beat you too it, also SLI isnt really a great idea because of negative scaling, extra heat, more power, SLI profiles, and driver issues. A larger SINGLE card makes more sense. Do two 560ti's out class a single 570? Yes, but in some games it performs worse because the game doesnt support SLI or the drivers dont support the game. It also means you NEED to have a motherboard that has 2 PCIe slots (more costly) and a bigger powersupply (another cost).
On a side note, while the HAF X is a nice case (I love it myself) it isnt very useful in a build like this, the HAF X is useful if getting VERY large graphics cards (GTX 590 or AMD HD 6990) or you are using an E-ATX motherboard.