I've just bought a couple of n3160 Braswell boards as was getting sick of poor performance out of the MIP's stuff I have.
If you don't care about the AES-NI instruction set's you can pickup j1900 based 4 port routers off aliexpress for under $100 (with intel 200 series NIC's no less).
The n3160's you can get for around 100$ but the cheap one's only have 2 gbit ports (rtl's).
The n3160's are only 6w at maximum draw and so far I've had much better results out of them than any of the MIP's or ARM stuff i've been using for the last few years.
The UBN stuff has been recommended in the past but when you can shift the l3 forwarding to a much more featureful and standard x86_64 platform and just hang your Wireless as dumb switches off of that I can't really think why bothering with the esoteric stuff requiring ttl converters to get up and running is going to warrant more investment at this point.
No one has yet to produce a proper x86 AC router - you can kludge one yourself with compex cards... I for one would totally buy one if such a thing were available.