alright this is kinda the way it is for those subs. I have used both of them in sealed and in ported enclosures. Depending on what you are looking for in a sealed enclosure those subs will sound very very nice but they dont really shine in the SPL area in a sealed box the same way the w7's do. If you go ported you will gain a good amount of SPL thats where these particular subs shine. You wont sacrafise much SQ if any also now the difference between the two is going to be more bottom end with the 13.5 over the 12. SQ will be the same between the two, so if you listen to rap I suggest the 13.5. A good amp to run those with is the JL 1000/1 if you got the cash.
as far as a box goes Try to go to a local JL dealer if you have one and see if they might have one laying around that they arnt using that they would sell you. If not get the specs and have a local shop that is reputable make one for you. I would not go with a pre-fabbed enclosure with those.