About 5 years ago I ended up a with a spare Klipsch driver from an RW-12d and couldn't scratch the itch of wanting to build with it.  I hadn't built a sonosub yet at this point and always wanted to try it, so I did.  To be honest, I could never stand the RW-12d.  I had two of them and they creaked and port chuffed like crazy, even without much woofer movement.  That said, when the driver was put in a better box, it really did well.