I have the Buttkicker LFE Kit. http://www.thebuttkicker.com/home_theater/products/bk_lfe_kit.htm
However other varieties are available as are other brands. I got a smoking deal on the LFE Kit locally from Fry’s Electronics because the department manager wanted to get rid of it since it wasn’t selling.
I only have the one transducer but up to 4 can be connected to one amp. Also any amp powerful enough can drive it if someone has a spare amp laying around however, other transducers can be easier to drive with an extra amp. The advantage I’ve found with using the dedicated amp are the controls especially the variable high frequency cutoff which allows me to control what frequencies get through to the transducer down to 40Hz. I generally leave it at 40Hz but there are some movies you would think have really low bass but actually don’t so I need to bump it up for those. This filter stops the “voice in butt” syndrome many other brands suffer from because they reproduce a wider range of frequencies. Also minimizes all but the lowest bass in the music from reaching your butt.
IMO one regular transducer is more than enough for several seats if they are connected rigidly in some way. It worked great on my futon in the apartment and now I just have it attached to a 2x4 sitting on the ground with the back legs of my seats sit on top of the 2x4. I was going to build a riser but when I found the seats were high enough not to need one to see over the M80s I figured I’d try out a simple approach and it works great. IMO it actually works better this way than directly attached to the futon. The system is more than powerful enough to shake the 2x4 and attached seats w/o any problems. Plus having it laying along the ground seems to absorb some to the energy so it’s a little less sensitive to changes in power making it easier to get the “volume” right. I also think having it on the 2x4 running along the ground “tightens up” the LFE by dampening any resonating. I have no doubt I could build a riser for two rows of seats and 1 LFE kit would be powerful enough to shake the whole thing as long as it was built rigidly enough.
Some, I imagine most, people turn them up to high especially to demo so people who haven’t had a chance to play with one might thing they are “just to much” or gimmicky, but I can assure you that when calibrated with the system it gives a very “lifelike” feel. Ask Sean how it felt when they were jumping the broken stairs in the Mines of Moria. IMO the Buttkicker enhances scenes like that in a way no subwoofer can w/o over exaggerating the higher bass frequencies.
Stop by and try it out some time. Maybe I can get Sean to do demo and review of it at some point.
Almost forgot. For those who poo poo the extra LFE outputs on some receivers I can say that the extra one makes using a Buttkicker much easier by allowing power adjustments using the receivers remote and separate from the real sub. Before I if I boosted the sub in the receiver it also boosted the Buttkicker which often made it overbearing.