Greg just bought a new house and he wants to wire it up for home theater all around the house. Leo says that the best thing is always wire in the walls. But it's not as important as it used to be thanks to Wi-Fi. Wi-Fi doesn't get through metal very well, though. Since Greg's house is already wired for sound in every room, its just a matter of upgrading it.
The best solution is probably to abandon the wires and go with a Sonos Wireless system. It'll cost him less and be better quality. He can use the existing speakers with Sonos Bridge, and he'll get an independent element to each room as well. The down side is that they are expensive. Another option is Chromecast Audio.