I've got an ASUS m5a99fx R2.0 MB and a saphire R9290x Vapor 4GB vid card. an 850W power supply, and an 8350 CPU. I'm wondering if I buy another video card (same thing I have) will it work ok mainly, second part. if I buy the 8GB version will it use 12GB of ram or would I be better off to go with another 4GB version? also, would I need to buy another Power supply like a 1400 Watt to power them both.