Marantz will be coming out with the Marantz ZR6001 and ZC4001. This AV receiver can be configured for a second zone of audio. But instead of using an RCA cable to send the audio signals, it can use the electrical wiring with DAvED (Digital Audio via Electrical Distribution). Up to six clients can be connected.
I wonder how well this works. Will it work across the multiple phases of most homes electrical systems? How does this handle interference on the power lines?