stereo to 5.1 sound

Hello, all

I have an Inspire 5.1 Sound kit from Creative Labs. It works fine,
connected to my DVD Player, which have an internal DTS decoder. But I
wish to connect it to a stereo source. I only want to use all the
speakers, doesn´t need to make a good signal division (like simulating
ambiental sound, etc..): the two left speakers can play the same signal
(the stereo LEFT) , just like the two right speakers (the stereo RIGHT)
and so on..

Question: Can I make this only with cables (making an "Y" cable)? Or I
need a small circuit to amplify the signal? And the subwoofer? How
filter the sound to send only low frequencies to him?

Thanks for any help,

Carlos Augusto Grahl