Music in every room, one source list
A speaker in every room is easy to buy. Making them behave as one system is the part that takes planning.
Audio is the part people underestimate. Done properly, whole house music means one source list, one volume behavior, and rooms you can group without thinking about it. Done badly, it means a different app for every speaker and an argument about which one is playing.
It starts with zones. Which rooms need to play independently, which ones always play together, how loud each one has to get given its size and ceiling height, and where the speakers go so coverage is even rather than loud in one corner. Amplification gets sized against the rooms rather than guessed at.
I use CasaTunes. A music server and matrix amplifier live in your own rack rather than on someone else's service, and there is nothing to subscribe to. Every room shows up as an AirPlay and Spotify Connect target, so anyone in the house can send music to a zone from their own phone, and stream counts can be raised later in the field as the system grows.
Integration with RTI and Lutron is built in, which is the main reason I specify it. The Pico by the door changes the music the same way it dims the lights, a keypad button can start a source list, and audio answers the same scenes as everything else. Dinner brings the lights down and the music up in one press.
Outdoor zones are part of this. Patio and pool speakers get planned alongside the landscape lighting so the whole exterior comes up as one scene, at a level that carries over conversation without involving the neighbors.
You run the speaker wire and mount the speakers. I size the system, lay out the rack, and program it remotely once it is powered and on the network.