Buttkicker transducer vs earthquake transducer vs ???

Hey guys, 

Wondering what you guys use for seat transducers and what luck you have had with them.  I currently have buttkickers but they seem spotty at best.  I just experienced earthquakes transducers in a demo.  It was great and seemed steady. Has anyone else used them and have they worked well for you? What amp do you use with them and what size transducer? I see that earthquake has two different models, a small and a large.