Hey there everyone

I'm planning to build the following rig, and by the way dont worry about profitability I'm 100% sure its profitable where I live:

Biostar TB250-BTC+ motherboard (cheap lga 1151 with 8 pci express)
Pentium 4440
4gb ddr4 2400
HD 120gb sata
8x gtx 970 g1 (I know they arent ideal but I bought em for a really cheap price)
2x EVGA850 BQ (850W 80 Plus Bronze )

The problem is: the 850w PSUs are bronze plus certified, that means at least 85% efficiency at 80% load and 82% efficienty at 100% load, and after doing some research, I found out that gtx 970 gpus usually draw 150w of electricity when mining, and Im planning to connect 4 gpus in each power supply.
Im pretty sure that the psu that will be connected  only to 4 gtx 970 will be fine because they're probably going to draw around 600w , but I am worried about the other one that will be feeding power to  4 gpus + the rest of the computer (processor, memory sticks etc). The 4 gpus alone might use 600w or more, and I'm afraid that when you include the power drawn from the rest of the computer the EVGA850 BQ might not be enough.
There's this one guy who told me I shouldn't worry because he knows someone who uses a 1000w psu to feed a 5 gtx 970 rig, but I still dont know what to do. I would hate having to buy PSUs and then returning it to the seller because I did a bad job picking my rig pieces.

What do you guys think? Should I buy one EVGA 850BQ and one Corsair TX850M (80 plus gold certification: 90% eff at 80% load and 87% at 100% load) instead?

Thanks in advance to anyone willing to help and sorry for all the English mistakes, its not my first language