A single 580 at max can draw some 250watts, core i5 draws 95Watts, 4dimms draws about 8Watts (1.6 ~=2x4 ~=8) 1 hdd ~10 watts. SSD ~5watts. dvd ~5watts. fans are about 5 watts each. Just keep that in mind, IMHO get a good motherboard, power supply, and case (you got that down). You can always upgrade if you have the right motherboard PSU and case ^__^
I would try to stay with a z68 because they are ivy-bridge compatible, work well with SSDs, and mATX layout they are pretty good. I am staying out of the power supply department but to help you make up your mind, There are POWER SUPPLY CALCULATORS that you can use to guesstimate the wattage you actually need for your build. (just check your video cards and see what they recommend for amperage/wattage).