"I'm getting used to MM, so having some sort of PC (hidden laptop) in my family room might work. I guess I would have to add some sort of card to decent audio output (or do PCs now come with that?)."
It depends on how critical the listening environment is, but you'll probably want to purchase an external soundcard for the laptop (either PCMCIA card or a separate USB 2.0 box). Creative Labs (soundblaster) makes both types.
I have my PC in my home office hardwired to the entertainment center in the family room, which then distributes the audio/video throughout the house via multiple amplifiers, controlled by keypads or volume controls in each of the rooms.
When we built the house, I had all the ethernet and audio/video distribution cabling put in before the drywall went up, so it makes it fairly easy to configure. It's strictly an analog A/V feed at this point, although the main PC can be accessed through the home network.
The weak link in my system is source control, so I'll be interested to see what you come up with.