Distributed audio
Wino,
There are a couple differnt approaches to a distributed audio system, it can be complex and expensive, or simple and cheaper.
Option 1: Distribution Amps, Keypads, etc.
There are several companies including Niles and Russound that make distributed audio systems. The distribution amps have a seperate amp channel for each speaker, for 6 zones you get a 12 channel amp. The amps are around $1k depending on the power and # of channels and you might need 2 amps for you system. Keypads in each room are about $100 each. You need a cat5 run to each VC/Keypad and probably need a customer installer to set this up. The advantage is that the keypads allow you to select any source in any room. My parents have a 10 zone russound systems in a large house. It is nice but also expensive.
Option 2: Stereo amp(s) and IMVCs.
I have the poor mans distributed audio system in my house. You use a stereo amp (or 2) and impedance matching VCs to power multiple pairs of speakers. All of the speakers connected to 1 amp are obviously playing the some source or "on the same zone". Many entry level receivers allow you to control 2 zones or audio (i.e. Yamaha RX-V663). Zone one is the main HT, zone 2 is another group of speakers powered by the amp. Higher end receivers (around $1k) have 3 zones of audio. If you can get by with 2-3 zones than this DIY system is much more cost effective.
Also If you are going to all this trouple, I would recommend a basic HT setup in your main room. You need a receiver anyway and any speakers will be better than the ones built into the TV.