Currently in use
Mac Pro 5,1 (Can hold 6 3.5 drives)
Xeon(R) CPU X5675 @ 3.07GHz
12gb Ram
512gb nvme on pcie adapter for OS
AMD R9 280x
Intel X540-T2 10gb Card
Currently testing with 3x 2TB drives
If it is stable, which I don't doubt as Mac OS is based on linux then I will slowly gut my parts machine and run dual cpu's with upgraded ram and max it out if needed.
I've always loved that generation Mac Pro case style and feel like HexOS will give it a good life. Love that you can fit two more drives if you remove the disk drive as well as the 4 drive slots. Unfortunately sata 2 speeds as it is old hardware :/. But if it becomes a bottleneck later on then I will probably do a custom build inside my rack with a lian li motherboard tray.