Depending on your CPU and overclocking intentions. A good quality 650W will be OK.
It really depends on your entire combination. Mostly CPU and GPU. My vega draws over 260W with my max overclock. My CPU draws 77W.
That's 337W for the CPU and GPU. I like to double the requirement for PSUs so I matched it with an EVGA G2 750W.
In summary, it depends on your GPU + CPU combo. Assuming you have a 95W(200W theoretical) CPU and a 260W max on the vega. A 750 or (850W) unit would be best.
Purists might tell you to look at the charts for each PSU and plot your system around it's max efficiency ie: 75%. But as long as you select a good power supply of tier 1 or 2,
with enough headroom, you'll be fine.