To hopefully fix my dropout situation (also have a turntable going into Sonos Connect and all the problems that go along with that), I would like to run ethernet cables under my floor so I can wire the Connect, a single Sinfonisk bookshelf speaker, a single Play:1 speaker, a stereo pair of Play:1s, and a stereo pair of Sinfonisk lamps.
The trouble is, this would presumably require a total of four ethernet ports, and my router only has three available. If I plug one of them into my modem (in router mode, of course), would that still work in the same way?