Well the problem with huge subs they only play huge sub sonic bass. ~35 hz and below. Anything over that, they play like ****. Kove makes execellent subs, but don't believe the hype.. They dont throw 2 inches each way for a total of 4 peak xmax. it's more like 2 inches xmax 1 each way. It might have a 4 inches of mechanical xmax but in no way does that mean it has 4 inches of linear throw. If you like loud ****ty bass, get your self an audiobahn. Sure they get loud but they sound like a sloppy *** doing it. Right now the car audio sub with the most xmax(DUMAX tested) is the adire BRAHMA. http://www.adireaudio.com/mobile_audio/drivers/brahma_series.htm
Check that site out and download the movies it's rather impressive. The 2nd sub with the most xmax is the Image dynamic IDMAX. And the sub that takes the # 3 slot is the audiomobile MASS.