^ + 1 for a Z68 board.
Also a +1 for the memory advice. Use low profile Corsair or GSkill Ripjaws X or Z to fit under a large air cooler if you are going to overclock.
Power supply is complete crap. The power supply is the most important part of your system.
For a single GTx580 go with a 600w power supply from Corsair, Seasonic, PC Power and Cooling, XFX, Enermax, Silverstone, OCZ or Antec. If you plan on adding a second GTX 580 in Sli then look for 850-900 watts from the same brands I listed above.
Since you are geting a K model processor I assume you will overclock. Add an aftermarket CPU cooler such as the fairly cheap Coolermaster Hyper 212 Evo. It will get you to the 4.5Ghz sweet spot of your 2600K easily.