Long story short: It can be described as a box, about the size of a breakfast-nook table. He wants to feed music into this box and get the music out (a speaker) but also vibrate the box such that someone in contact (sitting on it for example) will get vibrated from the music.
He want's as much of the gear in the box as possible (so no mounting speakers to the side)
My first thought is a pair of in-ceiling speakers or in-wall to create sound (imaging / audiophile quality are simply not requirements) but if I would do better with another arrangement: advice encouraged. Picked almost at random:
Then using a bass kicker (have considered a transducer. Thoughts?) to get the LF frequencies to vibrate the box:
Next: I'm guessing I'm going to need a low-pass filter to power the kickers; and then 4 amp channels (2 for the speakers, 2 for the kicker(s)). I'm trying to stay cheap here.
One thing I'm considering is a 10-year-old 5.1 avr from a pawn shop or the like with 5.1 inputs on the back. Then I'll take the source, y-cable the left and right channels, put a low-pass filter onto (say) the LS/RS inputs and use that to power the kicker(s).
Maybe these: http://www.parts-express.com/pe/showdetl.cfm?partnumber=266-252
Or do I need to go a different route? I could use the sub-out on an old 5.1 to feed an external amp: http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-383
I could use 2 such amps and the y-cable and filter; but costs seem to start climbing and I'm trying to stay as inexpensive as possible.