In-wall speakers are cool. The cables, speakers, and even controllers are installed in your walls and ceiling.
Conventional multi-room systems are sometimes more cost-efficient than pre-matched systems (below), in part because you may be able to use more gear that you already own. In a conventional multi-room system, you'll connect your music sources to a multi-room-capable receiver or a multi-room amplifier that can power speakers in multiple different rooms. A lot of today's home theater receivers fit the bill — multi-room capability, plus plenty of inputs for music sources like DVD/CD changers, satellite radio tuners, and more.
I hope you enjoy them. Let me know how they turn out.
Best of luck!