ok i m a bit confused Miguel, are you looking to ADD TOO your 12 CVs, or are you looking to replace them? If you would like to ADD TOO you current sub system, then I would say to get more of the CVs you have, or something extrememly close in sonic response to what your CVs have... reason is you ll likely end up with LOSS of sub structure by combining different boxes and expecting the i got more speaker boxes than i did yesterday, why does it sound like shit now??? there are so many variables that will affect your BOTTOM LINE (the sub output), by combining different boxes... you can take a ford and put a chevy tranny in it, but it dont mean it will do 100mph more than it did with the ford tranny.likely response is the ford will fall apart leaveing you sitting in the street on the tried and true chevy tranny.. lol
I would suggest you find someone in you area who has some Lab Subs or Some of Tom Danleys Designed Cabs, or another form of a horn loaded sub like the BDeaps mentioned.. and give a good listen to a horn loaded box. you would most likely end up with less boxes to carry/power/set up/ maintain, and MORE SUB Structure and output which is what you are really looking for if i read your first post right.
hth
Timmahh