The thing about multiples, many multiples, ... is the need for absolute driver quality is lessened.
When one considers the actual differences in design,.(be it Bl non-linearities with both excursion and drive current, soft-part non linearities, de-modulating ring efforts, etc ... all the above), moving from a single 18" pushed to the limit, to a set of four, or a set of eight ... the driver quality/output quality paradigm changes somewhat.
In these multi-sub systems, for nearly all the playback scenarios, the excursion remains so slight, even for high SPL playback. Obviously there's exceptions, with mammoth pulses of energy that can accompany the big effects. Then, by design, systems such as these handle them without encountering the ragged edge ... therein lies the beauty
Yep, some build the church for Sunday worship ... and the congregation is comfy year round. However they're a bit uncomfortably packed wall-to-wall on Easter Sunday.
On the other hand ... some build the church for Easter Sunday. edit; I do realize I'm preaching to the choir