I use the BKA 1000-N: http://www.thebuttkicker.com/home_theater/products/bka1000-n.htm
I calibrate it actively using the volume and the variable high cutoff which I usually set for 40Hz, the lowest setting, but which I have occasionally bumped up for some movies which you’d expect to have deep bass that really isn’t. I then adjust the volume knob to get the right amount of rumble by putting in one or more movies I use a benchmarks (LOTR FOTR Mines of Moria, or the opening of Star Wars III). Each of those have deep bass that I know when it feels right and proves good for almost all movies.
Having .2 a second adjustable LFE out on my Onkyo makes setting and adjusting the volume much easier if I’m alone since I can set it while in the seat rather than having to get up and adjust it at the amp and then sit down to test it again. It also makes it so I can change the EP500s SPL w/o screwing up the Buttkicker’s calibration.
On the occasions where the low bass I’d expect isn’t there then I bump up the crossover point, which is mostly trial and error. Only problem with putting the crossover to high is more of the musical bass can start bleeding over. The bleed over of the >40Hz music is fine as it actually enhances scenes, however bump it up to high and it’s just too much IMO.
I also passively calibrate it two ways. First is by using as rigid a mount as possible. I found attaching it directly to my furniture, not the mounting plate it sits on but bolting it to the furniture frame makes calibrating it harder because it’s actually to sensitive to volume tweaking making it easy to over or under shoot best volume. Also mounting it more rigidly dampens out resonance caused when directly attached to the furniture. For a single piece of furniture the mounting plate that comes with the kit works perfect. However, for multiple separate chairs I’ve found that just mounting the Buttkicker to a 2x4 and setting the back legs of my chairs on that serves the same purpose. The one standard transducer is more than enough to shake 4 chairs this way though I’ve only got 3 big ones. I imagine one transducer could easily shake a riser built to hold 6-8 chairs.
The other way I passively calibrate it is to cross over my M80 at 40-50Hz. This minimizes bleed over of musical bass into the LFE channel. Actually this is seldom a factor since it only reaches the Buttkicker if I turn the BK amp’s variable high cutoff above 40Hz.
The BK amp also has an on/off switch for the variable high cutoff so I can disengage it w/o changing the setting and it also has a fixed, on/off 25Hz low cutoff which I’ve never used.
AFAIK any amp can be used to drive one however due to it’s size I imagine it would need to have some power. From what I’ve read there are other transducer brands that are more easily driven by less powerful amps. However, most if not all of these (at least a few years ago when I was researching) were at the whim of the receiver’s crossover so if it was set as many do at 80Hz you got everything up to that point directed at your butt.
I was worried about what adding another crossover would do but I find that at the below 40-50Hz range there is no problem integrating the BK with the EP500 or I imagine any other subwoofer.
Not to make it sound like the BK doesn’t do higher frequencies well I actually got it about 2 months before my Axioms. So the BK was my subwoofer in my apartment running off the analogue out from my Oppo. It did an excellent job though it lacked any of the chest punch usually associated with a sub or full range mains. But I could crank it up w/o pissing off any neighbors. That is actually my most highly recommended use for the BK is someone who wants a true HT feel in an apartment, townhouse or even a bedroom w/o bothering the rest of the family. A BK running off the Oppo analogue out paired with my Sennheiser HD600s is quite a combo.
Finally, my amp started blowing fuses the first year. I called up “The Guitammer Company” and they shipped me a new one UPS with a return mailer for the old one no cost to me. Second one has worked fine for 3 years now.