There are many ways to potential set this up. The one iceman suggests is one. Other options would depend on what outputs your video sources have and what alternative inputs your Sony home theatre has.
If your video sources (like says DVD player or Digibox, which presumably are currently connected to the Sony theater system via scart) have HDMI output on them then there is another possible solution. If your Sony has an optical audio input and your Samsung TV optical audio output has there is another option again.
So IF your video source has an HDMI output on it AND your Sony and Samsung have the optical audio in (on Sony) and out (on TV) then you could connect your video source (say dvd player) to the Samsung TV via HDMI. This will get video and audio signals to the TV. Then you connect the TV optical audio out to the Sony's optical audio input and this will then move the audio to the Sony Home theatre. This solution would only require an optical audio out cable and give you the benefit of HDMI quality link from the video source to the TV (which should be better than scart) and still allow you to play the audio through your Sony system. This cable would be one like this
http://www.amazon.co.uk/TOSLink-Optical ... udio+cable
If your video sources had HDMI output but either your Samsung does not have an optical audio output or your Sony does not have an optical audio input but does have rca/phono left and right stero inputs, then you could use a box like this
http://www.ebay.com/itm/yardiX-HDMI-Con ... 35cdb97294 With this box you would go from video source via HDMI to this box. Video would go out from this box to TV via HDMI and audio would go out from this box to your Sony via left right phono/rca connectors. This would give you HDMI quality on video but audio would be limited to stereo and not full 5.1 surround.
I hope this is of some help and not just confusing things even more ? If you could give more details of what your video sources are (dvd, digibox etc) and what outputs those have and the model numbers of both the Samsung TV and the Sony system it might be possible to be a bit more definitive and clearer.