Upgrade/New Build Looking For Advice.

So I'm looking for some advice around a new build/upgrade, at the minute I'm running a basic unraid server with the following spec

MSI Z270M Motar

Intel Pentium G4600

32GB Ram 

Corsair RM450 

Samsung 970 500GB m.2 Holds my app data

3x 12TB Ironwolf

1x 4TB Ironwolf

Case Omen X 900

 

Now the first problem is I am running out of space and due to the case I really don't have many/any upgrade options once I switch out the 4TB drive for a 12TB drive. The second problem is I'm not running any parity drives due to the constraints of the case. The third problem is placement due to where the unraid server is place it has to be athletically pleasing and pass with the Mrs.

 

So far I've narrowed down a few parts which should work out but I am looking for advice on a few of the others. The parts I'm pretty set on so far are as follows

 

Case Thermaltake Tower 900 looks like I can have 22 3.5" drives plus a couple of 2.5" drives without too much trouble (well based on Thermaltake actually being able to supply the drive cages and trays which always seem to be on back order).

 

CPU AMD Ryzen 5 3600

 

PSU Something from the Corsair I range since I want to use this plugin

 

Primary GPU really not sure here I will need something basic possibly preowned just to boot the os and preferably with a blower fan since it will extract the air best.

 

Secondary GPU Something Nvidia so I can use plexpass's hardware transcoding again because of the case design a blower fan would be preferred can also be used just needs to be capable of 4k transcodes.

 

Third GPU not sure if I need this since once I'm booted the first time I can disable the unraid gui and use the primary GPU for a windows/Linux VM I don't leave these running all the time just spin them up when I need to.

 

HBA Card/Cards not sure which one/ones I would need but I plan on running 10x drives from each ideally. Not sure if there are any available with black PCB's?

 

RAM I'll just find pretty much any old ram that looks half decent.

 

Motherboard this is where I'm kind of stuck not sure if I need x570 or if x470 will do just fine I figured b450 is out of the question due to multiple GPU's

 

I will pick up some more drives as and when they are required 

 

2x Samsung 970 1TB m.2 for app data

 

2x Samsung 860 SSD's or similar for cache drives.

 

So if anyone has any suggestion hit me with them.

 

Cheers guys n gals.