There is a box design here, sticked at the top of the forum (Kappa VQ sub), that can be used with JL Audio 12W7. With this driver, you will get equivalent output/extension, and perhaps slightly better, than the Dayton RS 15" sub can produce. It is a more expensive proposition, but there you have it (smaller, pre-designed layout for you, etc.) if you so choose. That cabinet was designed specifically to allow for a wide variety of high performance drivers, and it's port is carefully chosen as not produce port compression, even with the extreme demands of a 12W7. Note: You will need 1000 RMS to power the 12W7 properly.
-Chris