Will the Dyn Esotar 1200 work in 1 ft^3? If SPL isn't a concern and you want a great SQ driver that will blend easily with your front stage and work in those airspace constraints it sounds like you've almost perfectly described the DIYMA R12. A 1 ft^3 sealed box is a great match with that sub IMHO and IME. It also reduces the pressure inside the box that has been the #1 cause of ripped cones on the R12.