I would like to run some sort of background service that streams my line-in audio to my home network.
I would like it to maintain the original quality as close as possible.
How should I go about this?
You could make the computer running the background service a Shoutcast server, and other nodes can connect to it locally.
I would recommend looking into a slingbox solution. This handy little device plugs right into your network with any standard cat 5 cable. It will not only allow you to stream audio, but it will also allow you to stream video when you so desire. Many people I know use these things and they watch their home TV from almost anywhere. One such person watches his home TV here in the US from overseas. Pretty handy and also pretty cool. I know this is overkill, but if something is worth doing... It is worth overdoing!