Let's say 100 watts in being consumed by the system, which makes 1280 watts for 6 GPUs. i.e, 213.33 Watts per GPU which is way above the TDP of the card.
I'm pretty sure it cannot be the case or else GPUs will shut itself down after a brief moment of working.
Moreover, you can still heavy under-volt your Sapphire so that it doesn't consume more than 100W from the wall per GPU, totalling to 850-900 Watts in total.

No, I have never experienced this kind of behaviour from a rig consisting of 6x RX 580s.
I have a rig which is similar to yours but they are Sapphire.
They never consume more than 750 watts even when dual mining at the highest peak.
I'll suggest you use claymore inbuilt commands for overclocking and undervolting and give it a try.
BTW, you are running from 120V outlet or 230V outlet?

I always settle for ASUS Z270-P Motherboard. Get some M2 to PCIe adapters and you are ready for 8 GPU motherboard.
Economical price and very reliable.

1. Yes, you can use the same bios mod that you use in a non-OC version for OC-version if they have the same memory brand.
2. The max performance you can get is 30 MH/s ETH and 800 MH/s DCR on dual mine with 110W power consumption which totals to a little over $2 before power consumption.

ASUS-Z270P. My go-to for any kind of mining rig set-up.

First of all, it is Zcash not Zcoin.
Use MSI AB and set the core speed at 1300 and memory at 1900, down volt using claymore commands and you may hit around 350 H/s.

Not at all.
More like 0.7 ETH per day but with today's price, that was like a lottery each day.

Calculation breakdown:
Network hashrate (31st Dec 2017): 5739 GH
Hashrate with 6x 1060s: 120 MH
Amount of ETH generated through Mining at that time in a day: (86400/13) * 5: 33230 ETH
Reward with 6x 1060s: (120MH\5739GH) * 33230 = 0.7 ETH/day.

Add this to the bat file:


for a N+1 number of Vega GPUs.

I'll recommend you to include the amount of downtime for reasons such as electricity down, Internet loss, miners acting up leading to crashes. Many people who come all enthusiastic to get into mining forget to take this into account. I was one of them. Moreover, check for the stability of the miners that you're going to buy. I'll definitely say that the price is really good for the offer but do your research before buying them and ask if he can produce some invoice for the GPUs which will make your RMA process for any GPU a less hassle in the future.

Did you check if the risers are posing a problem to your 4th GPU?
Try a different riser if you have some spares in hand.

Set -cvddc at 875 and remove -mvddc.
That's all you need.

RX 570 x 5 seems like the best solution so far.
It will do around 140-150 MH/s and 3500-4000 H/s on Cryptonight which is very good ATM.
With Dual mining, you can squeeze more profits.

Any Vega GPU that you can get your hands on and cost economical rather than paying premium prices for them.

I'll recommend 1070ti all the way!
I have both of them rocking in the same rig.
They perform close to each other in all the algorithms that I've tried but 1070ti also rocks in ETH where-as 1080 does not.

If you are looking for Ethash algorithm particularly, I'll suggest:
RX570 for USD 230-270
RX580 for USD 240-290
GTX 1070ti for USD 500
VEGA 56 for USD 459

Pick any GPU from above, they all perform extremely well on Ethash algorithm.
As you have price restrictions, I'll suggest you go with 7x RX570 or RX580s.
That'll give 210 MH/s on Ethash algorithm.

Now pick ASUS Z370-F which is a really good motherboard with easy 7 GPU support.
For CPU, I'll suggest going with 8th Gen Coffee Lake Processor (i5 or i7)
16 GB DDR4 2133MHz RAM
250 GB SSD and 2 TB 7200RPM HDD should be good for storage
Dual Corsair RM850x for PSU.

Bring the memory clock down and try again.
This error is because of excessive overlock.

You're trying to power 6x Vega GPUs which takes up to 300W per GPU.
So to be on the safe side you should think about Dual PSU setup as it will balance the load between the hardware and it'll cost less to own two mid capacity Watt PSU compared to one high one.
Moreover, I'm going to compile everything you need:
1) 6x 6 PIN Cables to power PCIe Powered Risers.
2) 6x Dual 8 PIN PCIe Power cable. One cable per GPU.
3) A 24 Pin MOB Cable, CPU Cable, SSD (If required).

Now, If you go with dual Corsair RM1000x it contains each and every component that I stated above and it is well equipped to handle Power hungry VEGA GPUs.

If using your PSU as a reference,
1) Use 6 VGA Inputs for 6 GPUs. One for each. One cable should have Two 8 Pin PCIe connectors for powering One Vega.
2) Now you have three VGA inputs left which can be used to Power six risers. As you stated the above cable in your last post. That will do just fine. Use one cable to power 2 Risers, thus accumulating all nine VGA inputs.
3) Rest of the connection is straightforward with CPU and such.

Note: Make a reading of Power output from your PSU and do underclock your GPUs for less power consumption to prevent it from overworking than its limit.

I'll recommend you to give Linux Distros a try like Simplemining OS, nvOC for AMD, ethOS, PimpOS.
They are already built with all the miners inside.

Well, something similar happened to me too.
I'm a miner and I don't know for what reason I bought the rumours that BitcoinCash will be termed as Bitcoin and original Bitcoin will become Bitcoin Classic and in that fuss, I bought around 1.8 BCH for 13 ETH at all-time high and the next day it was not even 7 ETH worth. What a bump! Never did I ever think about trading now.

You can get started in here.
http://btgpool.pro/
Use an equihash miner and you're good to go!