1070 cards have a 150 watts TDP , so for 6 cards + your system need min 150wx6= 900 watts + around 100 watts for ur cpu/mobo/hdd/mem , so your total system draw going to be around 1000 watts , if you know how to overclock and the same time undervolt your cards you will be ok with 1200 watts psu . I would not use 1000watts psu for ur setup...
Building mining rig to about 80-85 percent of a PSU's capacity is advisable to achieve maximum efficiency and stability .
If he runs at 60% TDP he won't be using more than 800w, so a PSU 1000w would be fine.
Also with oc and modded bios
There is no BIOS mod for NVIDIA.