Hey! I've got myself a creative Inspire t7900 + the DDTS100 Dolby decoder from creative. I've used the optical cable to connect my computer's audio out to the decoder and i do get sound, but the sound's very minimal from the rear speakers even though i've set my decoder and speakers to upmix to 7.1 .. why would that be? should i use the analog inputs perhaps? my motherboard outputs 8.1 sound. or does it make a difference when i use the co-ax SP/DIF?