You want to listen to your music in every room in your house and therefor you buy a network player, but they come always integrated into a speaker. However you already have a audio equipment in every room like the hifisystem or the stereo.
So I want to build a a little box where you only got the player and which you can plug into every speaker you want to. It will play your music over wifi at the same time in every room and every player can be the music server. So you have to push only one button at a one player and it will stream the music either form sd card or via line-in jack or bluetooth from your smartphone.