You might like to look at the Systemline modular range of products for your multi room install.
http://modular.systemline.co.uk/syst...homewhatis.htm
As a custom installer I can recomend this sytem. Like many others it distributes the A/V over cat5 cable the amplification is in the speakers. You can plug your legacy kit into the sockets in each room and play them in other rooms. Here is a list of features:-
Up to eight zone A/V output
Local/global capability.
Source can play in all rooms or a local room source can play in it's local location overiding the global.
Extended Zone.
Useful in en-suit bathroom type situations. The source is in the bedroom the sound comes out through the speakers in the bedroom and the en-suit. The volume level is independantly controlable in both the bedroom and the en-suit. Obvioulsy this is only an example. Both areas only count as one zone.
Expanded Zone.
Should you have a large room area to cover you can link multiple sets of speaker together to enable the sound to fill the room area obvioulsy the volume control effects all the speakers at once. (Up to six speakers)
5.1 surrond sound.
The system even has a 5.1 surround sound capability for use in the lounge/cinema room when used with the appropriate kit. (this would push your budget however!)
I could type for hours here but just ask questions if you wish.
Another multi-zone to consider is the AVNEX.
http://www.avnex.co.uk/
I am a distributor for them but to be fair you can fit them yourself. You can have up to 18 zones with this kit. However you need to obtain amps and speakers seperatley. Friendly pointer it can be a bit picky if you have SKY some of my installs have been ok others a "trial".
There are not many (understatement!) that can distribute HD video some can do S-video but most still only do composite the above only do composite.
Note! I am providing this info to help NOT to tought for business!