Am I reading the PSU calculator reports right, do you really have both AMD and Nvidia video cards in the same computer? If so, why?
I'd recommend some 20% headroom for a)aging and b)future needs. That said 550W seems like a bit on the low side. Sufficient right now but what if you get a 970 instead of a 960? As 600W can be hard to find, a 650W version would be the best choice.
Did you know that the Asus ROG PSU's are made by Seasonic, based on their Focus platform? A Seasonic Focus Gold can be significantly cheaper, at least here. There's a Seasonic Core 650W as well.