Set-up is very important for these. You have to get the volume just right and also set the crossover properly as well. Clark Synthesis generally tries to run full range with their unit and I don't like that. Buttkicker is much better in my opinion. I haven't tried out the Crowson system yet.
Also, I would recommend them for movies, not music - at least not to people on this forum. Maybe if you want even more bass in your car then you could use one in your ride.
If you want a demo that will certainly impress you, try out the D-Box Odyssee motion simulator:
http://www.d-box.com/
I have one in my living room and am seriously considering buying another one for the smaller theater in the back of the house. They blow away even the best tactile transducer.
