I don't own the VMPS larger sub, but I heard one extensively a year ago at the Midwest Audiofest. I spent most of the weekend in the Bolder/Teres/8th Nerve room guarding a mini keg of beer
The larger was one of the best musical subs I've heard. Wayne from Bolder set up the room using an 8th Nerve roompack. He also used an EQ on his QMS sub amp set with some RTA laptop program.
I suspect that the Larger sounds so good because of the very large internal volume as well as the additional mass (mortite) loaded onto the passive radiator. I"m guessing this additional mass might make the passive SEEM much larger than it really is.
Why two different size active drivers can mesh so seemlessly, I haven't a clue....but they sure seemed to me that they did. Again, maybe it is the "tuning" using the mortite on the passive that helps with this.