All you have to do is to add a AudioFloat Controller to, and I recommend, a helper object, that will drive the subwoofer itself...
I also recommend to toy with the sound file a little so that you can kinda over-exaggurate the basses (depending on what you need), then use this to drive the animation along the original sound file to play in the animation.
As soon as I finish rendering something here, I'll rig it up and post it up here so that everyone interested can play with it...