BIOS Settings!!!!
-> Enable 4G Decoding and set PCIE x16 and PCIE x1 Link Speeds to GEN2. Done.

The main issue is that Claymore is not able to detect any GPUs even if they show in Device manager. It's probably the driver issue.
1) Download the latest AMD 17.5.2 Beta Drivers and extract it in your rig. Don't install driver yet, just extract.
2) Go to safe mode and uninstall the drivers with DDU. (You won't be boot into safe mode if Above 4G Decoding is on so turn it off.)
3) Now, boot the system and manually install the driver by going into device manager -> update driver of GPU option -> Select a driver from disk -> and pointing it to the extracted driver folder.
4) Once all the GPUs are recognised, restart and make some changes to bios, i.e. enable above 4G decoding, set PCIE x16 and PCIE x1 link speed to GEN2.
5) Start the rig and power up miner.

-->> If you are having trouble setting up the bat file in claymore, just send me your eth wallet and I'll configure a bat file for you, you just need to place that bat file in claymore folder and execute it.

The highest one of my cards ever got was 81.9% and most of all are between 70-77.5%. (RX570 Pulse 4GB and RX850 Pulse 8GB).

Try this
1) Disconnect all GPUs and connect video input to integrated GPU and see if you can boot into Windows. If yes, check if it's installed as UEFI and not legacy. If its UEFI and not legacy then go to next step or else install Windows 10 again with UEFI support.
2) Download latest AMD drivers 17.5.2 and extract them, don't install yet. Just extract them.
3) Turn off and connect 5 MSI GPUs first with correct PCIe configuration and then connect the sixth different one on the last lane.
4) Connect your video input to the first GPU.
5) Turn on make some bios mods - 16x PCIe lane speed to Gen 2 and so for 1x lane speed. Don't turn on 4G Decoding yet.
6) Start your windows and manually install the driver via device manager by pointing it to extracted driver location. (Make sure windows update is disabled)
7) It'll install all the drivers perfectly.
Restart and turn on 4G Decoding. Done! Your 6x GPU rig should work perfectly.

I've a VGA which doesn't dual mine at all even after removing most of the tweaks. I'm wondering if I can manage to dual mine 5 cards and single mine 1 card within the same instance of claymore rather than two different instances running because it causes a lot of fluctuations in MH and it keeps crashing after an hour or so. Any help will be appreciated. Thanks!

Depends on many factors mate, like the temperature of GPU, your whole cabinet, ambient temperature. I don't think this should pose much of a problem unless the temperature is in range. You can always desktop monitor your computer from home via Teamviewer to check on temps and shut it down remotely if you feel sceptical about it.

This happens because your MOB is not able to transfer data effectively with the riser in between. You have to make some bios changes so as to make the risers work perfectly. Change x16 lane PCIE link speed to gen2 and x1 lane speed to gen2 too. Then try your riser. It'll definitely work.

I guess aliexpress is good option to consider for risers atm. You can always opt for a faster delivery method and they will reach you in a week.

According to my experience, I've been using SATA to power three 1x to 16x USB risers and I haven't bumped into any power issues, moreover, the cables are running pretty cool.  Can you provide me with the info on where you found that powering 1x to 16x USB risers is not a good idea as they cannot handle that much power draw?

Get 580s, they are great for dual mining! I would recommend 8GB Variants as the DAG file gets bigger time by time, 8GB will be long lasting and moreover, they are easy to sell.

Give Windows 10 a try and as I posted earlier about tweaks from 1stminingrig.com. It includes disabling a lot of windows 10 background services, but as with my experience right now. Windows 10 is rock stable and my rig is currently doing 180 MH/s ETH and 3400 MH/s SIA dual for two straight days.

I guess with the growing trend right now with crypto currency and more coins getting added each and every day, Profitability and mining with any of the cards can yield a good amount in long term.
But still go for the option which is cheaper around you.

I ordered 25 PCIe Riser pack and received it in just 4 days. (I opted for a faster delivery service for 13 USD) In spite going for premium delivery service, my cost per riser is 80 percent less than what they are selling in my country. So it's a perfect win. If we take an account of the quality of the risers, they are top notch.

Check you PAGE file size - it should be more than 16000 MBs. Keep minimum 16000 MBs and maximum 20000 MBs. A majority of the miners rely on virtual mem to keep the process quick and it requires a good amount of size allocation.

I want to lay down everything that I have experienced and learned a day before to set up my 6x RX 580 Sapphire Pulse 8GB in Windows 10 Pro with Asus Z270A Prime MOB.

1) Install Windows 10 Pro w/ only integrated GPU & no Dedicated VGAs connected.
2) Check for updates of OS.
3) Install drivers that are required for you MOB to work efficiently, by going to your MOB support page. [UPDATE to latest BIOS]
4) Now, go to 1stminingrig.com and search for their windows tweaks. Apply all of them.
5) Download latest 17.5.2 Relive drivers and extract them in C: Folder, don't install yet. Just Extract them.
6) Shut down your system and connect all of 6x VGAs.
7) Go to BIOS and make sure you make the following changes:
- x16 Link Speed: Gen2
- PCIe Link Speed: Gen2
- Disable HD Audio Driver (We don't need audio and in some cases, audio driver shares a lane and it may cause problem with one VGA)
- 4G Decoding: Disabled
- Memory Remap: Enabled
Start your system, go to device manager and it should show six VGAs with Microsoft Basic Driver.
9) Just go to the primary driver that is connected to the primary x16 lane and manually install the driver by locating it to driver folder in step 5.
10) It'll install Driver for all 6x Cards.
11) Go to BIOS and Enable 4G Decoding now so that there are enough available resources for all the cards to work together.
12) Done! It should boot up with 6 cards detecting and up and running.
 

You've got a Nvidia Card and miner is using Opencl to create a DAG File. Opencl is for AMD and CUDA is for Nvidia. Can you post more information on your VGA and the miner you're using?

Awesome build man! I really loved the video of 48x GTX 1070. So colourful. Keep up!

Hey there, don't mind me but I'm wondering how you can check the quality of your risers? Is there a guide to it or something like that. Thanks!

Sapphire RX 570 Pulse 4GB (Hynix): 1140/1999 - core/mem with 2:1500 straps copied till 2:2000.
ETH: 28.5 MH/s with SC: 470 MH/s [Pulling 135W from wall]

Anyway, we gotta do what we gotta do, taking good care of rigs and maintaining them even if we have to sacrifice our comfort a bit. In return, they do our computational work and we are rewarded with freshly made coins. So, let's keep the hustle on.