absolutely...
toughpower series from thermaltake is a excellent unit..
let's see..
a system equipped with this parts..
only consume
562 watt in gaming mode..
taken from : http://www.tweaktown.com/reviews/5826/msi-radeon-r9-280x-3gb-twin-frozr-oc-in-crossfire-video-card-review/index23.html
so your toughpower is more than enough to handle 2x 280x in crossfire mode, and still have plenty headroom for other parts..