Dolby 5.1 decoder, Amplifiers and sources

[frostie2001uk]

I plan on getting a dolby digital 5.1 decoder for my lounge,
separate DVD, Video and sky sources as well as separate audio
sources.

The sources I plan to connect them to the KAT5 switcher (at least I
have time to save up for it!!) BUT how do I connect up the 5.1
decoder?

I assume the Zone associated with the Lounge (or where the decoder
is) would have the Video sent down the cat5 to the KAT5 receiver and
the audio split off to the decoder?

If SWMBO just wanted to watch, say, Eastenders, she probably would
just want stereo not the full 5.1, would I need to use
another "Zone" or would the audio continue to the TV anyway and
I'd
just mute the TV when playing in glorious Dolby Digital 5.1 and vice
versa.

How about listening to a CD or other audio? Would I use the decoder
as the amp for audio as well?

(NB. All sources and decoder in situ with the switcher - Node 0)

Sorry for the long post......

Neil