I have an "upstairs computer" (the one in the office) and a "downstairs computer" (the one that's now sitting by the chair next to the Dining Room fireplace). The "DC" is an old Dell laptop with a wireless network card. It has its audio jack connected via cable to an old stereo receiver in the cabinet. This feeds two little bookshelf speakers hidden behind the books in the bookcases [that I built] that stretch across the wall above the fireplace [that I extended out by a foot into the dining room in my first -- and last -- attempt at bricklaying].
I've been using iTunes a lot to check out various audio streams using the "radio" feature in iTunes. I currently have a playlist of radio streams that include Bollywood and movie soundtracks, various "Ambient" and "Electronica" signals, a variety of Jazz, Latin, and Tropical channels, and all the Classical music I can find. It's quite an amazing variety. If I hadn't already given up CD's as an obsolete medum I'd be buying a lot more music.
The quality is not up to CD, but, hey, I'm not payng extra (yet) so I'm not complaining. I am learning a lot about stuff I would not have otherwise been exposed to.
For a while I was copying down already-ripped or purchased tracks from the UC to the DC when I discovered the Sharing tab in iTunes "Preferences" page. With sharing turned on on both machines, I can display in the DC's iTunes a list of the CD's and tracks I have already ripped to the UC; this includes the tunes and albums I have purchased from iTunes (back when I was purchasing iTunes music).
I have noticed that when I attempt to play a "purchased" track from the UC on the DC that I have to go through the process of "authorizing" the DC to play the track, but that's OK for now.
Anyway, I think this is a pretty neat feature; I can play the upstairs music anywhere I have another wireless networked computer in the house. I guess I should have read the iTunes documentation sooner!