In that case, I would need a MUCH bigger PSU. Does it make sense to just go with a huge PSU from the start? This was meant to be an economical build, and adding another PSU and getting a 3 card motherboard would ramp the price up. But anyways, what motherboards would you recommend?
New PSU pick: http://www.newegg.com/Product/Product.aspx?Item=N82E16817152036
I know people hate Raidmax, but i haven't had any bad experiences with them yet.
On the Wiki page, they use one 600W PSU for the 2 card build, and if I want to upgrade to 3, I could just add the 450W "modular juice box." That would be a lot cheaper, so that will be the way I go, but with a more powerful starting PSU.