You like the ZimaBoard 432?-Shades
It's a great little unit, plenty of power for something like pfsense, at the moment I've just been playing with it seeing what its native OS is like, I'd need to redo my networking a little before incorporating it running pfsense but I don't have the time right now.
CasaOS is a container management front-end based on Debian, got a lot going for it but I found it rather flakey so just installed DietPi along with Portainer.
Have also installed ProxMox on it and run pfsense through that but it didn't really leave enough resources for the other things I was looking at running, 8GB version would have been ok though.
You might want to look at the ZimaBlade, same sort of thing but cheaper because you add your own RAM, (DDR3 SO-SIMM).
Downside is only one Gbe port but decent Intel secondhand PCIe cards are easy to get if you don't already have them lying around.
Base model with 2 core CPU is only US$64 with the 4 core at US$96 - they're pre-order ATM - looking back this probably would have been a better choice for me since I have spare RAM I could have used and therefore bumped up on the CPU.
Btw, don't know if it's still applicable but a first order on a new account got me a 30% discount, so the 432+SATA Y cable was ~US$115.