2. not much better, they are designed for sq but still with an spl gain
3. subjective, if your running a Kicker CVR no, because u could get 3 for the price, XX.X, yes, ive heard amazing things about them in the Snail shell
4. from what ive heard yes
5. not much further but they usually are better
in the future im thinking about selling my 3 12's and getting a single 18" and putting it in powered 4 sounds next doing, the centerfold, the problem is i know nothing about it except its rumered to be a 17 db gain over sealed : O, but im not sure if its a single or dual, so i'll have to wait and see