Good morning Tom,
Supercube II-III were discontinued many years ago. They were replaced by the supercube 8000, 6000, 4000, 2000
The 6000 is the II replacement, 4000 the III... I personally use a 6000 in my studio and (14' x 22') and have plenty of power. Now, about reproducing a 32' stops... forget it. The specs (from Deftech and other manufacturers) are more or less exact... probably that the sub vibrates at 16hz... but you won't hear or feel it rear... what you will hear are harmonics.
Many reasons for that... but just the wave length of the lower C (a bit more than 70 feet/21 meters) makes its difficult (if not impossible) to reproduce in a normal room. Also, to feel it, you need to displace a lot of air, have the room for it etc.
In the church installations that I did you can feel the 32' (with some well recorded sample sets... another problem, most microphones stops at 20hz)... but the subs are large, heavy, with 60lbs magnets with very powerful amps.
That been said, I like my DefTech, and you will get of course more bass (lower frequencies) than a sub advertised at 32hz... in my room, I usually can feel the 32' effect down to A1 (so around 27hz.
Audio specialist will better explain all the physic and why it is so hard to reproduce such low frequency. What I like about the DefTech is that it is musical, not boomy... you should like and the 4000 should be enough (the 6000 is more powerful and use it when renting an Hauptwerk organ for concert in a church and is powerful enough (not perfect), but good enough for a 400 seats church).
My 2 cents