Let me cover the mounting question first. If you look on http://www.thebuttkicker.com/how_to_...ngs_shake!.htm
the first one showing "Slab Floor" with the board, the original feet from the sofa (which I plan on changing to isolation pads) and ButtKicker on it is pretty much what I'm doing as well. Just a couple of 2x8s make it all happen. http://www.avsforum.com/ubb/smile.gif
As to comparison... well, as so many have mentioned before there really is no comparison. I couldn't figure out why, though, since they were more "musical" and "stronger" didn't make much sense to me. After all the Bass Shakers are pretty strong, if you ask me. Now I know the difference, though, and will see if I can explain it any better for you.
The Bass Shakers provide a buzz, kind of like a vibrator, that changes frequency a bit based on the tone of the LFE being generated into it. This in itself is pretty darned cool and I certainly recommend it for folks to try out considering the fairly low price of these. I found I could lower the volume of bass on my sub somewhat because of this little extra added "oomph", but not by very much. nice enough to make sure I didn't blow away my upstairs neighbor, though, with rumbling bass on those "U571" depth charge explosions when watching that DVD.
The ButtKicker, on the other hand, has less of a vibration effect and more of a rumble. It is certainly capable of hitting much lower bass than the Bass Shakers can. The Bass Shakers have something of a feel like the couch was vibrating, the ButtKicker has more of the effect that you feel that rumble more in the pit of your stomach making the effect a bit more dynamic and less kitschy. You can feel the dynamic range a lot more, making the Bass Shakers seem a bit one sided on what bit of shaking it produces. Yet it is just as capable of shallow vibrations and being very responsive to changes in soft or higher pitched selections. I really am able to lower the volume on what I listen to with such a dynamic bass response.
The differences are pretty strong but very hard to describe. Kind of like listening to a high quality recording in mono, which sounds wonderful, then all of a sudden comparing that to the same recording in stereo. Kind of eye opening, but a very difficult effect to describe to someone who has only ever heard mono before. It kind of feels like the Bass Shaker is a keyboard that only plays one octave but the ButtKicker plays 3 octaves. You can do great things with one octave, but 3 really lets you open it up.
Is it worth the $700 for it with a single amp as compared to a whole bunch of Bass Shakers with a few cheap amps that you could get for the same price? Hard to say. Depends on how important that expanded dynamic range is for you. Lots of folks can be very happy with a $200 receiver that does most everything they'll ever use it for, but other folks barely bat an eyelash at spending $4000 for that extra bit of dynamic range and extra goodies that a high end receiver will get them. It was certainly a worthwhile purchase for me and at least now I can understand more of what all those other people are talking about in their reviews!