Hello i've bought as follow

Intel Celeron G1820
ASRock H81 Pro BTC R2.0 LGA 1150 R2
6 X Sapphire Radeon NITRO+ RX 570 8GB AMD OC Dual 580
4gb DDR3  Ram
Raisers
and i'll make the rig here custom

the question is ,
-what power supply should i get to handle all this gpu and MB ?
- i've saw alot of videos ppl replace gpu cables with other cables they say its better is that true ?