Okay, it's not really a guide because it's peculiar to my hardware and I don't completely comprehend why it's working and I took a lot of wrong turns to get here. But it works!
Here's some background: I work from home and I like to have music playing in the background downstairs, not in my office. For some reason, it takes the edge off the cabin fever having music playing in another room rather than blasting in my face. At first I did this by tuning in an FM radio station on my receiver in the living room. Later, I switched to using one of DirecTV's music channels because they're commercial-free and genre-focused so I don't have to listen to a crappy Josh Groban song to hear a nice Derek Trucks Band track.
Last year, I discovered Spotify's streaming music service and became a huge fan -- so much so that when I was asked to install a music system in a friend's wine bar in Carroll Gardens, Brooklyn I went with Spotify and a wireless-enabled laptop, which also let me program his music playlists remotely.
What I really wanted however was a way to play Spotify on my great-sounding living room home entertainment center and to be able to control it remotely from my office upstairs. If I could do this then not only could I indulge my fickle musical tastes by choosing what's being played but I could also mute the background music during business calls (yes, I play it loud). My HE center also plays music in the back yard, so bonus.