[KAMiKAZE]

maybe u're right Luciel such a audigy card would cost me 66-70 €
(upto 8 channels) and my current card is useless then *snif*
or I heard of cables which split the output sound (example of such a cable:
my_sound_blaster_output_for_front_speakers------then_two========one_of_them_to_sub_and_one_to_aux_ from_stereo_system

I'll ask in shop if I have time or call them they should help me (now I know what to ask for and I'll ask if the sound quality is worse if I split(if possible)

@Quall999: maybe I'm totally wrong, but isn't aux only able to transfer stereo?