Bottom tier spec, noisy, power hungy. Most seem to take 2.5" disks and one takes 3.5" disks, you need to find disk rails and disk controller may not be happy with consumer sata disk unless you were planning to buy brand SAS disks.
Fans in those are quite small and need to push lots of air trough, I don't see how to make them quiet easily, fan headers are propietary and sizes most likely are not standard.
If you need to cheap out, then maybe some aliexpress mobo with used xeon + ddr3, hba card and standard atx tower etc.
Does physical fw/router bring extra security compared to locked down software firewall and vpn?