my power supply can handle more i have 850 gold and run 4 rx 560 and i have empty slot in my power supply with 8 pin and the rx 560 need 6 pin
any Suggestion
560 consumes about 60 watt or 75 max as far as I know, so you have about 350 watt free taking into consideration 500 watt you are consuming with your 4 GPU-s and the mobo and other parts. With 350 watt you have room up to a GTX 1070 ti if you want, or a RX 570/580 Sapphire Nitro+ 8GB. So fill it based on your budget.