I don't have a AV Receiver, and I bought a Blu-ray Home Theatre System which I want to work with my cable box. It only has a HDMI output, no input. But it does have an unfamiliar input called Optical. I want the speakers and everything to work along side with the cable box so i'm wondering if I need to return it and buy an AV Receiver with speakers instead? I'm not sure how the Optical connection would work or if it's Optimal for me. My cable box is HD, so i'm not sure if the Optical connection would give it Quality of an HDMI or Component. What should I do to get the set up that I want? Thanks in advance!