The second zone is best thought of as a separate two-channel analog audio and s-video/composite video pre-amp tucked inside the 990's chassis - it will let you use any audio or video input with a separate display (such as a TV with audio/video inputs, an extra stereo amp and speakers, or whatever tickles your fancy) completely independently of the main 990 system. The second subwoofer pre-out is a convenient means of connecting two subs in the main system - a simple way to think of it is as a built-in splitter cable (both sub outputs get the same signals, as does the balanced subwoofer output).