H.T. newbie - Subwoofer questions...

Hi everyone, I'm new to home theater - just purchased a Denon AVR4800 receiver, surrounds, center channel and subwoofer. I hooked everything up and it works GREAT, but I have a question about the subwoofer. It's a Klipsch KSW-12, and I would like to use it for both home theater AND just audio. The way I have it set up now it's only being driven when in THX or surround modes because I don't have my main speakers (Martin Logan Sequel electrostatics) plugged into it - they are just hooked up to the receiver. If I understand this correctly, I can unplug my MLs from the receiver and plug them into the right and left outputs of the sub and then plug the sub into the right and left outputs of the receiver so it will then "catch" all the low frequency signals before they hit the MLs, thereby eliminating the ML subwoofers, which is fine by me. Is this correct? Also, would I just leave the other connection to the subwoofer output of the receiver so when I'm watching a movie, it will process the low freq stuff that way? What would happen if I was listening to music in stereo mode and then switched to 5 channel stereo? Would both the front speakers and the subwoofer output be driving the sub at the same time??? Any advice would be greatly appreciated. Thanks!