These low power PC's are opening up new opportunities for UPS's, namely that they all run off low voltage DC (nominally 12V) and open up the possability of a 12V UPS. It saves on the inverter required in the UPS, and increases the overall efficiency.
For a device like this with a variable input voltage you can run it directly from a 12V SLA battery, and then keep the battery topped up with a decent mains charger rated to higher power than the PC. You can generally do the same thing with access points and 12V network switches, and any 5V devices can be run from a $5 step down DC-DC converter.
The only problem I've had with this method is 3.5inch USB Hard Drives, as they usually require a well regulated 12V supply. For those I bought a fancier buck-boost DC-DC converter, they were a little pricier and harder for find than, but still quite reasonable.
In the end you may have 30W worth of devices hanging from the SLA batteries, then just buy a multistage charger rated to the next higher power - eg 30W = approx 2.5A @ 12V, so get a 3 or 4amp charger. You can expand to as many parallel as you like, all it does is slow down the recharge time.