I auditioned the JL Audio F113 & G113. OMG! They redefine subwoofers.
Phenomenal, incredible, soul-rattling impact in low frequencies! You probably won't find them discounted anywhere like you can the RT-12D. The price is STEEP, but they can afford to charge it because they are THE BEST.
The Gotham will make your grandchildren sterile, spoil the milk you plan to buy next week, and back all the nails out of the subfloor in your home!