With technology changing so quickly these days, spending money putting speakers in a wall is a waste of time and money. Putting pipes that you can re-thread new cables through would be better.
Our house was fully cabled when it was built, tv, network, isdn sockets in all rooms. The lounge has speaker connection points behind the sofa and channels running through the floor. When we moved in 9 years later, all the technology had changed, so we couldn't connect our speakers to the sockets but we could run our wires through the channel and change the socket.
In the basement media room we use wireless speakers - cable problem solved