Recommended power rating for a GTX 580 is 600W. 700W will be plenty.
The Antec 1200 is the case I use. It can fit any size motherboard and any size graphics card in, including dual-GPU graphics cards like the HD5970. It can also fit up to 12 drives. For cooling, it has 3 intake fans at the front, 2 exhaust fans at the back, a fan on the side (can work either direction) and a huge exhaust fan at the top. Basically air will constantly flow through it, so the system will always stay cool. Plus the case has a built in control for fan speed (and the blue LED lights) so it can either be quiet or loud and powerful, depending on what you're doing.
If you're getting the system now (instead of waiting for the next generation of Intel CPUs), then you just need to look for a LGA 1156 motherboard, depending on if you want a
quad core Core i5 Lynnfield or a
2+2 core Core i5 Clarkdale with integrated graphics (there are faster ones, but I only linked the cheapest one for comparison). Assuming quad core, a P55 motherboard would be best, like the Asus Maximus series. Here's the selection from
Scan.