Overall the build looks good and I think you are going to be very happy with it. The Intel® Core™ i5-2500K and the Asus P8Z68-V make a nice pairing and the Cooler Master hyper 212+ is good for dealing with the heat from overclocking or even every day use. About the only concern I have is with the SSD you have selected. I havent personally heard anything about this drive but my experience with ADATA memory has left something to be desired.
Everything looks good but the psu. There are some people on here that will say an 850w psu is fine for dual 580's, but if you go to the Nvidia and/or EVGA forums they say the opposite. That 850 may push two of those cards but it's going to leave you zero headroom not to mention the life span on that 850w is going to be short seeing how it's going to be running balls to the wall and get hotter than a fried egg.
Also this case down below just came out on newegg a few days ago and it has better cooling imo than the 600T not to mention it has built in fan controllers and the option to add even more fans later on. This case is going to be a big hit imo with what it offers for the price. There's also a black version of this case.