Craig, can you give us an idea of where you put it and its gain setting. I'm also curious about the size of your room. (Think you posted details somewhere.)
Give "Hyper-ballad" by Bjork a spin. 34hz 37hz 40hz never sounded so good. A bass reference test with pretty vocals attached. Lol.
A different song without a sub altogether. The bass line adds a foreboding dark undertone to the track to match the lyrical content. Good argument for subs in stereo listening. Would be interested in your impression of the M100s with and without subs on this track.