My experience with this type speaker systems low frequency extension (no experience with Vandersteen) is limited adjustability and most importantly limited placement. Modern subwoofer control technology can make possible placement, as it relates to room node reduction, more relevant than subjective sonic pairing. Using long inexpensive line level cabling and mounting subwoofer/s on dollies to find that rooms best subwoofer location/s can greatly reducing room nodes without sacrificing the sub/s gain and maintaining optimum equalization.
https://www.audiogon.com/listings/subwoofers-velodyne-dd-12plus-black-2016-05-17-home-theater-91201-...
With one or two DD Plus (used 10"s for less cost) one would have the flexibility to attain extremely accurate and flexible integration. You'd also have the ability to model the presentation of most any other subwoofer you desire and store it in one of six custom EQ'd presets as well as other remote controlled adjustments such as volume and phase which can be made from the listening position. Phase often changes from track to track on a single album.
Go to Velodyne.com and compare their Digital Drive Plus User's and Interface Manuals pdf's to most any other setup and placement information supplied by other manufactures.