BoomGames has reviewed the RumbleFX 3D Sound Amp from Evergreen Technologies.
I would like to state that music sounds good played through this unit - for that I would use it in a heartbeat. Good for all those times "20" just isn't loud enough... The bad part is, it has a power cord! With it's size, you have to think that they originally engineered the unit to have 4 AA batteries right in the top flat panel and it was scrapped somewhere down the line. But I'm just speculating.