" Part of me feels like being daring and looking for a pair of drivers to use that may equal or possibly improve
performance "
Why not, after all, adventures can have happy endings (albeit, woofers can be expensive off the shelf!). The only drawback is you don’t know the TS parametres of the original woofers. Do you have a friend who can measure the remaining woofer, so you know what you’re looking for? If not, you might as well take Van up on their offer.