First mining rig

Im going to build my first mining rig but i have some qestion about my setup ;
MOBO : MSI Z170A GAMING PRO CARBON or MSI Z270 GAMING PLUS ? the Z270 is newer and cheaper 30$ but only 6 gpu and couldnt find any mining opinion about it
CPU : Intel Celeron G3900
RAM : Kingston HyperX FURY 4GB DDR4 2133MHz is 4gb enought ?
GPU : 3x SAPHIRE PULSE RX 570 + 1x GIGABYTE RX 470 from my PC ( after few months and first payout will buy 2 more RX570 and another PSU)
PSU : Corsair CS850M 850W is it enought for mobo, cpu and 4 gpu's ?
HDD: cheapest hdd i will find (i think no need ssd)

The biggest qestion is PSU enought for 4x GPU ?



thanks for all help