For all of you who have doubts about AE, it’s quite easy to set up a listening test to hear the difference between mono and stereo bass. If you want, your can also invite your mother to the listening test if she's interested.
First, set up your subwoofers in a stereo configuration on each side of your main speakers, and obviously connect them in stereo. Open a DAW and put an HPF on the master track, and set it at 80 Hz and with a 24 dB slope. Import all kind of different music tracks you want to test, and just listen to what happens to the bass under 80Hz in isolation when toggling between mono and stereo on the master tracks (most DAWs should have that functionality).
To me, it's easy to hear the effects
@Thomas Lund describes as
“big”, “open”, “free”, “pleasant”, “light” in favor of stereo bass, in opposite to mono bass, which is described with words like
“unpleasant”, “claustrophobic”, “small”, “restricted space”.
How much of a difference it makes is of course highly dependent on the audio production, and if they contain stereo bass information or not.