I just built my pfSense box with the Extended model.
It has been really stable so far. It’s using the Intel I340-T4 and it can route gigabit at ~60% CPU usage with Suricata and pfBlockerNG enabled.
CPU temp is a bit high: 50C idle and 62C when routing gigabit for a couple of seconds. However, the fan is extremely quiet, probably because it spins at a very low speed by default. There’s an option in the BIOS to pin it at full speed, but I did not change that. So I don’t know what the lowest possible temps are.
It also runs on the onboard 16GB eMMC, so no SSD needed.