I need a budget pfsense box

Define best.

I like the Wyse 5070 extended for a router. Has a x4 PCIe slot for a network card. Not the cheapest, but very low power.

Any HP, Dell or Lenovo SFF desktop with 4th gen or higher CPU. Probably $50.

If you only need two interfaces you can go with the micro boxes and put wired networking in the wifi slot.