Hi Simon,
It was me just thinking aloud really.
Having improved the signal from PC to amp with a fibre optic cable, I was thinking that from amp to speakers the signal would degrade a bit because of the use of wires.
I've just read a review of the Logitech Z5500 speaker system and you can plug more than one thing at a time into it ie DVD player, TV, games machines and so on
In fact one chap suggested using both analog and optical connections to the PC so you can use all the applications of the sound card.
Thanks Martin