I agree with using TrueNAS, I currently have a Fujitsu Futro S920 that can host two mirrored SSDs, it is a cheap build if you don’t have to host any services, you can found details here: pietro.in/en/posts/futro-s920-proxmox/

For more powerful hardware but still staying in a cheap build take a look at an HP 800 G4 mini or a ThinkCentre M910x both can host two NVME disks