Figured I'd add my 2cents
I just refreshed my system. Since OMV4 I've been running a hacked up Dell Optiplex 9020 i7 / 16GB RAM with a SSD for OMV and a 8TB drive internal.
I acquired a stack of 8TB NAS drives from work, & I've had a bunch of extra components lying around so figured it was time to put them to use & buy the rest.
Case: Fractal Node 304
MB: Asrock H370M-ITXac (6 Sata connectors!)
CPU: i5-8600
RAM: 16GB DDR4
HDD: 4x 8TB
SSD: 2x 900GB MLC Server drives
NVME: 256GB - System/OMV
So far it's awesome, but the stock fractal node 304 fans are just basic 3pins, so a bit noisy. I'll adda controller or upgrade to PWM later.
It's stupidly overpowered, but I do run multiple 4k streaming now and again, and will use it as my NVR soon too once I can get a Coral TPU at a reasonable price. I do my entire home network in docker containers, so I end up needing more power than the old dell could provide. The Node 403 case is great for the price & has room for a GPU for later needs (real time transcoding)
x3 8TB drives are mergerFS & snapraid data, x1 is snapraid parity.
The SSDs..I don't have a need for the speed at the moment, but one is for my docker appdata, the other? I dunno yet.