I doubt our 460w PSU will suffice. The Radeon RX 580 requires at least a 500w PSU. Check out the Corsair CX500.
I completed this build with a CX750 and a Sapphire RX 580 this weekend. Everything seems to be operating smoothly so far. I would recommend the modular CX650 as it was tight squeeze with the modular CX750.