After having tested the transmitter/receiver combo I received a few weeks ago, I decided to add another future-proof receiver (cinch, coax, toslink/optical) to connect my secondary system to my PC. The plan is to add one more with a pair of active loudspeakers (these here) further down the road. That should cover the whole apartment, to boot.
Audiofly has devised a system that broadcasts music instantaneously across 50 meters (indoors)/100 meters (outdoors) without the hassle of having to set up a network system of any kind, which I am reluctant to do. Plug the USB transmitter into any USB port, plug the receiver into any wall outlet and hook it up to your amp, active pair of loudspeakers or whatever can receive input … and enjoy instantaneous transmission to up to 4 receivers.
Easy as pie.