You can carry AC3 through one digital port (coax or optical) but the reason they give you 2 on the hoontech module is that modern computer sound cards generate 2 stereo signals (one for front, one for rear), unless you're playing an AC3 (I.E. Dolby Digital 5.1) DVD. Theoretically, you could carry 50 channels of audio through 1 digital port, but it's useless unless both the sender and the receiver can decode and use all channels. In this case, 1 port is a 2 channel dolby digital signal for front output, and 1 port is a 2 channel dolby digital signal for rear output. Your best bet would be to plug one digital out from the hoontech to the digital in on your receiver (for DVDs), and then get 2 stereo minijack-> dual rca adapter cables and then plug those into the appropriate channels on your receivers 5.1 input(for using EAX enhanced apps/games). Just my $.02.