I bought some Aura Bass Shakers about 8 years ago when Parts Express had a sale. Currently, I have two mounted on the bottom of each of my two couches. All four shakers (connected in parallel) are powered by a 70watt subwoofer plate amp
from Parts Express. With the gain set just above 1/4. I know it's crazy to have four 4ohm shakers connected to an amp that is only 4ohm stable, but it has never been a problem. I could easily turn them up more, but the impact becomes more than I prefer.
At the moment, I have the front couch's shakers disconnected, so just the two in the rear couch are on the amp, which is adjusted closer to 1/2 gain. For me, I didn't want my shakers to have a super hard hitting punch. I am only using them to supplement my 18" subwoofer (Cerwin Vega Stroker18). With the mounting location I chose, it seems to have the strongest impact. I had tried mounting them on the front of the couch frame, on the rear, one on each end, then finally just added the board in the middle and it had the best overall feel and impact.
I just found this site which seems to have a somewhat equal method of comparison for several different shakers: Shaker Comparison
Hope it helps someone with a future purchase decision.
One other interesting thing I've done is to screw one of these shakers directly to the floor or a wall. It then radiates actual audible sound in the typical subwoofer frequency range. I haven't tried taking measurements, but it is a neat way to add some bass to a room without taking any floor space. Certain spots on the walls seemed to have much better effect than the floor. By vibrating the whole wall or floor, the sound starts to become a whole lot more non-directional than I've heard with some box subs.
Vistadelloco, how'd you add just small thumbnails instead of the larger pics I've attached?