I've got an ASUS r9 390x. I am contemplating buying another one for Crossfire however, with AIB RX 480s coming out (hopefully soon), I was thinking of going that route for a lower power consumption Crossfire setup. Asus R9 390x models are going for about $300 used on eBay. I'm concerned that my Seasonic 850 watt PSU you will not be enough so Id probably be tacking on another $150 dollars to the $300 R9 390x. Other option would be 2, $275 RX 480s once the AIB ones are available. What do you guys think?