Yes or No? Your opinions needed

I am running a pair of Q 15's on a PAI-2000.1 @ 1ohm sealed. It's deep and its loud, specially in a civic hatch.

I don't want to lose my back seats if possible, that's why I opted to go with the Q's sealed from the get go. The box before displacement is 4.9cuft on the dot. Do you think I would get more output if I closed off one of the speaker holes and added a few 4" aeroports, tuning the box to 33hz and popping in a single 15" BTL D1 to run the amp at .5ohm? I am not sure how long the ports would have to be or how many I would need (3-4), so I am not sure if after displacement it would be an ideal enclosure for a BTL. I would be losing half my cone area (-3db) but porting it (+3db) with a louder sub and slightly more power since I would be dropping to half an ohm.

Thoughts?

If that wouldn't be an ideal setup, then I will keep the system as is and maybe lose the back seat later on down the road. If that happens, I would probably run a pair of 15" BL's tuned to 33hz in 8-9cuft @ .5ohms on the PAI-2000.1...or a single 18" BTL.

More thoughts?