First build...

Hi 
Sorry if this is already posted somewhere but I was unable to find it with search...

I'm building my first rig and can't figure out if I need 2 PSU's  or not, if I plan on running 6 x (GTX 1060 or 1070) GPU's

I plan on buying the following.

MB: ASRock H81 Pro BTC 
CPU: Intel Core i5-4460 Haswell 
RAM: 16GB Kingston HyperX Fury DDR3-1600
GPU: 6 x GIGABYTE GeForce GTX 1070 ITX OC - 8GB or EVGA GeForce GTX 1060 SC GAMING - 3GB
Riser: 6 x Nuovo PCI-E Express 1x A 16x Extender Scheda Alata Adattatore SATA Cavo USB 3.0
PSU: 1 or 2? Club 3D CSP-X1200CS - 1200W PSU - 1200 Watt

Do I need 2 PSU's or can I settle with one or do I go bigger like the EVGA SuperNOVA 1600 G2 - 1600 Watt


Also would it be a problem if I ran 3 x 1060 and 3 x 1070?

any advice would be appreciated, thanks.

- Theo