I have a 7000 system with the speakers in two rooms. Also I have a sub woofer, but want to make sure I get the best from it. This may seem like a stupid question, but what is the best way to wire it up. At the moment I just take an extention form left channel and link it straight into the woofer. To complicate matters there is a switch on the side of the woofer which says 30 watts/15 watts, and I would like to know what this does. The speaker is marked cambridge soundworks. I appologise to anybody out there in advance that this is not a driect B&O question.

I'd leave it as it is if you're happy with it. Generally the budget subwoofers don't tend to have filters in them (a filter would normally allow you to ease off some of the load from the main speakers).