I have a Stentor III, recently bought a PSA sealed - 18inch, not the prettiest thing but for films it is miles ahead of the REL, considering the performance on tap its great value. For music I'm still with the REL (music is more about timing and less about explosive deep bass in my experience

).
It is heavy and big but just in different dimensions to the stentor.
Whatever you do, try to get REW and a microphone if you have options it's super great for placement. If you've only got a single sub, then I did a reverse sub crawl on mine.
Place the sub at the location of the main seat, moved the microphone to the various location options in the room and ran the REW sweep. Finding the location with the flattest response I placed the sub ran REW again this time with microphone at seating location to verify I got the same response (it did) and teaked the location an inch here or there to perfect the location.
Multiple smaller subs + a transducer for the shakey not hear bits is another option although it has its own placement/configuration concerns.