I did my calculation for psu also, 700-750w is about exactly the usage, no much head room.. 2x250w(R9 290) + 80W (i5 3570k) + 80w (MB, 2x4G ram, 1SSD, 2HDD) + 30w (5x fans + led). No dvd drive, all usb devices pluged on monitor (confirmed powered by monitor). So pretty much 700w is everything...