I'd port 4. lol j/p, I think the Type-x's sound better sealed. They handle kick-bass OK in either enclosure, but if you want sq I'd go with the 4 sealed X's. If you aren't worried about response curves go ported.
Well im looking for good SQ but still want it loud but have limited space to work with (its hard trying to fit big boxes through my trunk opening although the trunk is 13cu. 4 sealed on 4800rms (rated power on underrated amps) 4 JBL Bp1200.1's vs 2 ported on 2400rms (2 JBL Bp1200.1's) should still be about as loud if not louder i hope. As long as it will still pop my ears and make it hard to breathe ill be fine... trying to get somthing on par with my old 2 dd9515F's setup 12cu box... 40hz..
For the L7, definitely go ported. I think the output will be somewhat similar, but from my experience with these things, you won't regret porting them. They sound a ton better in all aspects. I have one 12" in a 2.75cuft @ 32hz right now, and I really have minimal complaints. It gets loud (obviously) but doesn't sound as bad as a lot of people seem to think. JMO
I say go with two sealed or ported more room to move the box around to find the sweet spots of the vehicle less power needed to get loud and no need for mega batteries and huge alternators to do so....the only way id do four subs is if I had a van or something with a ton of space in it to move around freely
lol well right now i have 2 12" L7s in a 4 cubic foot box tuned to 38 hz but i saw the begining of Gorrilla zoe's hood nigga music video and he has 4 12"s L7s in a sealed box and i can't believe how much his car shakes
that the subs wasnt making the hood move from the video of hood figga thats especial effects it would take more than that to make that hood move like that especially those cars that are pure metal and not pieces of plastic and fiberglass