One very powerful subwoofer can produce a great deal of output. That does not automatically mean it will produce consistent bass across several seats.
The room creates peaks and nulls
Low-frequency wavelengths interact strongly with room dimensions and listener position. Different seats can experience very different response from the same single subwoofer location.
Multiple sources create design options
Using more than one subwoofer gives the designer additional placement and optimisation tools. The goal may be smoother seat-to-seat behaviour, more headroom, a directional bass strategy or a combination of these.
More is not automatically better
Quantity without placement, delay, level, filtering and measurement can simply create a more complicated problem. The bass architecture needs to be designed and commissioned as a system.
Choose the architecture before the model
We first decide how many low-frequency sources the room needs and where they can work. Only then do output capability, enclosure type and infrasonic ambition determine the actual subwoofer models.