Go to partsexpress.com and look up the Dayton Reference Series HO subs. They will fit nicely and they are very nice subs. $250 delivered for a pair. not cheap but they are build like tanks and should handle anything you want to throw at them. I should have mine up and running soon and will post response. Look on another thread for the pics.
I have a pair of the JL 10w1v2-4 they sound great. I have the same box you do, I have filled the inclosure with polyfill and running a JL 250/1 amp. Sounds great.