5.1 Surround Sound to PC Speakers

A few years ago I bought some logitech speakers for PC. There input is the Green, Black and Orange output on a 5.1 surround sound card, or you can use the logitech adapter with converts 2 phono leads to Green, Black and Orange:


However using this you can't use them with a DVD player to get 5.1 surround sound.
Is there surround sound or an amplifier which outputs to the PC jacks (Green, Black and Orange)?
So I can use my speakers with my DVD player (Coaxial Cable), TV, PS2 (Optical Cable).

Thanks,
Sephers

Moved from the Lounge to Multimedia Hardware.