the only thing i ever thought of selling the btls was i can sell them only for 100$ less than i payed.

lets say how many dbs will increase by building a box that is twice the size? (same car, same amp)

Ask a term lab that question for an accurate answer instead of some from me or others on this forum.

150 is EXTREMELY hard to achieve FYI.

Good luck.

2 18s qs sealed would sound so good. it would be ear candy with no fatigue. but if your going for 150 then thats a negative.

You really should take the advice given and stick to building a new box before selling or buying new ones. Back when, I had a splw-15 that I hated until I put it in the right box. It blew my mind how much louder it was.

If your 18" btl isn't giving you what you need, it's the enclosure, not the sub. Those things are ridiculous. In the right box, it should be more than enough.

You can do it! 150 here you come.

power, electricals and knowledge here, will get you to your goal...