A single 15 would be cheaper to purchase than the pair of twelves, even with having to build a new box. However the pair of 12's has a cone area advantage over a single 15 (960cm2 vs. 810cm2) and therefore the potential to give more output. The enclosure for the 15 would be roughly the same size as your current one so you're really not going to save much there. Plus you already have a nice enclosure for the 12's so making that choice is a bit tough. If it's a budget problem the single sub is always the best choice just because it's cheaper and typically easier to build for. If there's no issue with budget, space, or build complexity (I know there's not, I'm just trying to lay it out for everyone's understanding of the thought/choice process) then the decision will come down to personal preference.

Larger format subs (15's, 18's, etc.) are definitely fun to play with, but they're not always practical mostly because of enclosure size. 18's are a blast but you need a big SUV or van to really utilize their capabilities, even for one in some cases. 10's and 12's are probably the most popular sizes just because they're so much more practical in their space requirements. For you, it's a tough choice when you go to weigh out what you want.

 

eventually ima put a Bpillar wall anyways, whenever i get another car for a DD. plus iv seen alot of s10 blazer 2dr and 4dr with bpillar walls with 18s so i know its do'able

 

Oh yeah, it sure is. It comes down to whether or not a person wants to do that much modification to their vehicle and if they want to spend that kind of time and money to do so. Unless a person is vehemently meticulous about how they do the installation the vehicle is permanently modified to get a wall put in which is another problem for some people.

I think it will be awesome to see you put a wall in. I've always been a big audio enthusiast but could never bring myself to entertain the thought of doing a wall and follow through with it.

 

walls are long term projects anyways i think, but once i get the new stuff ima try to move the old stuff into my room >:] and since its a 5 channel amp i dont need to buy surround sound for my new TV of course playing it within reason though.