The 20.1 is no more inefficient than the 3.6, so I wouldn't worry about amplification. If people put bigger amps on it it's likely because it *can* play louder, not because it needs them to produce the same SPL as the 3.6. Also, as someone pointed out in another thread, the 20.x's are only 5" wider than the 3.x's, there's more of a difference in height.