I picked up a 200W home audio powered sub yesterday at an auction for $20.
Brought it home and ran a couple of wires off the bottom cabinet speaker of the JP, through a line level converter and into the sub....
The effect is amazing
We had it cranked and it makes the dinosaur growls and other effects awesome. My wife went crook upstairs and complained that the windows were rattling!
Great fun if you have a spare or cheap sub lying around.