Personally I'd avoid the sub. 42lbs? Doubtful. KLH isn't exactly the best when it comes to either the sub or speaker market. You may wish to look on Parts Express website for the Dayton Audio 10" powered subwoofer.

For the KLH, it includes an amp. 125W is peak power. It is the maximum output. It probably requires you to put on the feet for the sub but not much else.