Video Card Upgrade Help

So, first thing first I'm not all that knowledgeable on computers. I want to upgrade my card from my two Radeon HD5670 (Crossfire) to a Radeon R9 or Radeon RX 480. I don't know if my Motherboard is compatible though. Or if I have a good enough power supply or not my computer specs are as follows:

PROCERSSOR: Intel Core i7 CPU 930 @ 2.80Ghz

SYSTEM MEMORY: 3 Memory Module's at 4096MB DDR3

MOTHERBOARD: Alienware
Product # 04VWF2 Version A02

VIDEO CARD: Radeon HD5670 1024MB x 2 (Crossfire)

Please help. Can I run a R9 or a RX 480?