Audio Systems: Square and Round subs, kicker solobaric, hifonics amp


Question
Hi, I currently have 2 12" Kicker Solobaric 2 ohm L7s being pushed by a Hifonics BXi 1606D.  I would like to get a third Solo Baric, so my system will be louder, but I can get a 2006 12" Kicker CVX for a cheaper price.  Both of the subs have the same RMS and peak power rating.  Is it  possible to have the three in the same box, or should I just get the solo baric?  If it will work out would it make my system any louder?
Thank you.

Answer
YOU HAVE TO MATCH SUBS. you cant mix and match different kinds or it will sound horrible.  if you want to get another sub it must be the exact brand, size, ohms, model number, version, etc.

now if you have the dual 2 ohm version of these subs (model S12L72) then you must have them wired so the coils are in series and then the 2 subs are in parallel. giving a 2 ohm load to the hifonics amp. this amp is rated for 1100 watts into a 2 ohm load so each sub is getting 550 which is pretty good, you could technically add 2 more of these subs to this amp and it would still push them respectfully at 400 watts each.  
The box actually has a alot to do with how the system sounds and performs and if its not right, even the best subs will sound crappy in a poor box. what kind of box do you currently have (ported, sealed, other) and is it built well with no cracks or holes or anything?  is it within the recomended specs for these subs?
Also how to you plan on adding this 3rd sub if you get it, you cant just cut a hole in your existing box and stick it in or you'll have worse sound then you have now.