While comparing these two subs, a few things stand out for me right off the bat: 1. B4+ is twice the price of the PB2+ 2. B4+ uses four 25-31 PC+ speakers which individually are 25Hz low, whereas the PB2+ goes as low as 16Hz. So my question is, how do they rate the B4+ to be under 20Hz when the component speakers themselves are 25Hz? Obviously because of the # of speakers, the B4+ would pot out way more power than the PB2+ but it seems like the lows would not be as low as the PB2+. Am I incorrect here? But for twice the price of the B4+, wouldn't two PB2+ speakers put out more power and go lower than the lows of the B4+? Thanks for any help. P.S. Does the low end frequency really matter or is the total RMS power more important? I know that the human ear cannot hear under 20Hz... but you would "feel" it - so I thought that the lower that the lows can get would mean that you are getting a better sub. The power output would depend on the amp, more than the speaker itself. Do I have an o-k understanding of this here?