optical audio in typically requires optical audio out.
try this...if your HTPC has analogue audio outs plug into the sony using the same (labeled) inputs as where you connected the optical cable. ie: if the optical cable is plugged into the optical TV input plug the analogue cables into the analogue TV inputs. connect the bedroom TV to the SACD or Video 1audio outputs. with any luck the receiver will see both connections and pass the analogue through.