Music Streaming to Overtake Downloads
You have introduced a false dichotomy. Not all streaming services involve "listening to music selected by someone else." Napster, for example, lets you listen to any song you want, any time you want. They do offer "radio stations", but, very importantly, when I get to a song I don't like, I simply hit the "Next" button and it's gone. Try doing that with satellite radio.
Current Recommendations For a Home File Server?
Actually, as long as you need heat in your house, how can efficiency possibly be an issue? Isn't all of the lost power simply converted into heat, which is something you need anyway? 100% of the energy is being used for something you want.
Based on this thinking, in the winter-time I've stopped harping on the kids to turn off the lights when they leave the room.