Well I think the only issue that you would have is that PSU (assuming it's the Corsair VS 650w) only comes with 2 x PCI-e power connectors and I believe the R9 270x requires 2 x PCI-e power connectors per GPU. This would mean that you need 4 x PCI-e power connectors, which you could use adapters to do that with, but I wouldn't recommend it that way. It's up to your on what you would like to do, but I'd recommend against using the PCI-e power adapters. The PSU should be able to handle 2 x R9 270x's and the FX 6300 (assuming your not OC'ing too much).