I just ordered a pcengines apu1c4 Mainboard - around 230 EUR all inclusive.
I first had an used 5 years old firewall, but the apu1c4 was slightly faster and I calculated that running 24/7 the cost for electric power (which is quite expensive in germany) will make the apu1c4 cheaper than the old firewall hardware.
I have a 100Mbit/2,6Mbit Cable Internet access. pfSense runs with snort, some firewall rules, openVPN and squid proxy.
I had havp running with squid, but this slowed Internet access too much. The rest runs ok for me.
Conclusion: An pcengines apu1c4 with 30GB mSATA SSD, Case, powersupply is faster, uses less power, is more silent than a 5 year old hardware and is cheaper if you use it for more than 2 years.
Edit: Details: https://forum.pfsense.org/index.php?topic=59555