I have heard the Bose system is hard to modify. I can use either a line or powered input to my subwoofer, it has its own amp. Can I just come off the rear speakers to power it, or will that cause a problem with the Bose system?

 

The BOSE system is not hard to work with and around if your know what your are doing.

It will not work well using the output signal to the BOSE speakers. To do it with no issues to the system you need to install use a Line out converter like the Audio Control LC1i then run your separate amp to the sub woofer. I would be careful with your gain and set it very low.