I am trying to connect my laptop to my Coby HDTV for a great monitor, while at the same time get the 5.1 dolby surround sound from my laptop through my RCA 5.1 surround sound box (not the cable "rca"). I have an optical cable, HDMI cable, and an rca to rca cable. Display to HDTV works but I get no sound from surround. Any thoughts?