If you use ARC to pass your audio from your Cable/Satellite Box connected to the TV via HDMI then you will loose your surround sound. It will down sample anything passed through to 2 channel to comply with HDCP.
You will need a TV with a real HDMI output that repeats HDCP to pass-through 5.1 channel. BENQ seems to make one, but can't find it in the US.
From the HDCP page on the DCP site:
"<font size="2">HDCP receivers may render the HDCP content in audio and visual form for human consumption. HDCP receivers may be HDCP repeaters that serve as downstream HDCP transmitters emitting the HDCP content further downstream to one or more additional HDCP receivers."</font>