I powered 4 GPUS (5870, 5870, 5970) off of a single Rosewill Capstone 450 watt, but I also slightly undervolt and slightly overclock my GPU's. I have a kill-a-watt to measure power consumption. It was about 10% over spec, but still ran just fine with no noticeable effects.
That calculator grossly overestimates power consumption. That said, a quality, high efficiency ~750 watt power supply should power those cards fine, even if you decide to overclock.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182264$115 minus 25% promo code = $86.25. The Capstone line from Rosewill are excellent power supplies (They OEM from SuperFlower, which is currently a very highly recommended manufacturer. Jonnyguru.com recommends these PSU's)
Also, pick up some PCI-E power splitters. They will be invaluable, as using molexs can lead to fried adapters because you are overloading the wires. There are more wires in a PCI-E cord to disperse the load.
http://www.newegg.com/Product/Product.aspx?Item=N82E16812198018 $3-$4 each.
http://www.newegg.com/Product/Product.aspx?Item=N82E16812198016 $4.50-$4.10 each, can be found slightly cheaper on ebay when bought in volume.
