Advantech for pfSense

Why not just pickup an hp290 and a 2 or 4 port intel nic? You can get it all done for about $150 or so.

Examples

https://www.ebay.com/itm/HP-290-p0043w-Slim-Celeron-G4900-3-1GHz-4GB-RAM-500GB-HDD-Win-10-Home-Black/113384273741

This is what several folks including myself and @JDM_WAAAT run our pfsense on.

Here is a great resource on the HP box: