It really depends on how much power costs you and how low power you are wanting to go.

I've just built the equivalent of a SYS-E200-9B pfSense box I feel pretty good about. Can't go wrong with <10 watts at the wall. It was about $300+$25 in RAM. We'll see how it truly performs though as I certainly haven't put it through its paces yet.

Honestly it's probably fairly comparable to the N3150 for all intents and purposes. The big difference is that the N3700 has a better GPU clock (pointless for this purpose) and turbos faster (could make a bit of a difference). It's still unclear if the low-ish clock speed is going to bite me.

I was really thinking about picking up C2XXX something or other. But they are over 3 years old now and they suck a crapload of power (comparatively), and I just couldn't make myself pay such a premium for them.

I never saw Intel's NUC's suggested. Is that because they all seem to only have one NIC?

I'm pretty sure that's basically it. Almost all of them are super lean on NICs and not very expandable.