I have a dual recliner/loveseat with 2 buttkickers and 2 Clark Synthesis Platinum Transducers wired to it. One of each under each chair. The buttkickers are hooked into the LFE and the Transducers into a mixer taking the signal from all speakers (7 channel surround right now) and feeding into a left and right transducer.
It takes a while to adjust them to mesh with your speakers instead of overpower them, however once you do it, you'll wonder why everyone doesn't.
And once you have them on and have been using them, if you ever turn them off during a movie, you'll feel like the sound just went flat.
I'm still in the "build" process, but once I'm done I'll post pics and notes on the install. ...just don't hold your breath for them, because with my busy life, it takes a while to finish projects like these...