Call me crazy, but I use the Yamaha SW118V sub with the AudioSource Amp3 in 400W bridged mode. I paid about $200 a piece for both items refurbished. The 18" sub is linear to 20Hz and only starts distorting at 15Hz. With the 400W amp I get up to 120dB of undistorted bass.

Of course not everyone has room for a 7 cubic feet box in their home theater.

Leszek