Well the last few years of VMPS Bran seemed to be sourcing a number of things from PE, so the Lab15 may be one that he used since I doubt he had the volume in the last few years to be getting them OEM from Eminence.
He did use the TC Sounds drivers and called them the OMG upgrades as there were a number of threads on them. Unfortunately, the frame on the TC Sounds, and possibly the Lab15 as well, may not fit the woofer cutout in your sub box. I recall Brian did discuss some issues with using some of these later upgrade drivers with some of the standard VMPS sub cabinets. I would expect that John could be able to help with this, although enlarging a woofer cutout isn't really that difficult.