You are paying far too much for that motherboard. Look at Newegg or another retailer.

The graphics cards are overpriced for the 4GB version.

1x 4GB DDR4 RAM is probably fine, so it's up to you if you want that extra stick.

Running 12x 580s on 2x 1000W PSUs is going to be a bit of a stretch, even after messing with clock settings. Did you check if you'll have enough connectors for all of your cards and risers?