If you want to buy hardware for this and not reuse something old, Intel embedded ITX boards are the way. Chipsets J1900, J4125, N6005, or the newest N100. Cheap

If you want to buy hardware for this and not reuse something old, Intel embedded ITX boards are the way. Chipsets J1900, J4125, N6005, or the newest N100. Cheap, low power, x86, standard PC parts, great performance (magnitudes more than SBC-s/RPi-s).