I am actually considering the construction of twin bass cabinets underneath the 2251's...housing TAD 1601c or JBL 1500AL like Merlin used. I could be waiting a long time to find a pair of TAD 2404.
Good luck finding the 1601c, probably harder to find than the 2404 which in my opinion is already too hard Better off trying to find b's. Enjoy, they look very nice