You should go ported or vented with those...talk to a local shop and get them to do you one with a 28 Hz tuning or have someone design one for you and build it yourself...which would be much much cheaper if you have the right tools...
there my recent answer was about as specific as what u are lookin for in ure box, i meen obviously ure goin for spl, cus itd be rediculous to go for a SQ with two solo 12s, unless u just roll that way, but yeh ill just say it again, itd have to be perty decent size