If I were building such a setup ~ heres what I'd do;
cross-compile APCUPSD/NUT for the ROUTER, and use the networked status update for the PC.
1. Alot of cheap routers have USB ports these days.
2. Many of can run embedded linux
3. If the PC is off - the other devices have no warning of impending doom...
I'd say you need atleast 360 VA ~ but due to outright distortions of truth from low-grade mfg. I'd use 500 VA units.
You know - if the PC needs to always be powered;
Use a DC-DC ATX PSU!
No wasteful conversion of AC-DC-AC-DC again.