Try connecting the stb directly to the tv via the coax input. That runs the signal thru the tv's ATSC tuner, out the optical cable, and into the avr. That's what I do for OTA tv and I get discrete 5.1 (when broadcast) perfectly. My blu-ray player and AppleTV2 are connected to the avr via HDMI and a single HDMI out to the tv. The tv's speakers are always off so blu-ray movies and anything streamed has it's audio played thru the avr via the HDMI connections, and tv has it's audio played thru the ATSC tuner and out to the avr via optical. I use a Harmony remote to control the system and it's components with a single push of a button to switch between inputs.