This is one of those deals that is only a deal if you need it. When setting up PFsense, Untagle or Sophos I like using small form factor desktops. In the past I always seemed to have one laying around that was good enough to meet the specs required. If you needed to buy something for this use I have found these to work well, They are small, but they offer a lot of functions, compatible with a broad range of CPU, four DIMM slots, M.2 slot, two PCIe slots:
Dell-Precision-Tower-3000-Series-3420-Spec-Sheet.pdf
Major limitation for actually using it as a workstation, the PCIe x16 slot is