My experience is a limited one, but here it is: I had a pair of Kef Reference IIIs for several years, and loved them; I think the floor on them is something like 40 hz. Very fine controlled bass. Then I got a pair of von Schweikert VR4 gen iiis., which have a floor of 20 hz. What I noticed was, as Tvad suggests, something nearly physical, in particular when listening to, say, the acoustic bass of Arild Anderson: it's the thud under the low notes that I really heard--or felt--for the first time. Then there is the orchestral/choral music of Arvo Part. In any case, I can't be sure whether it was the 20hz that made the difference, the speaker design apart from the 20hz floor), or the different flavor of the two speakers from 40hz and higher. But the vrs broadened the lower spectrum, and I'm speaking as someone who doesn't go in for cranked up bass that smears everything into a mess.