I currently have a 15w0 with sealed enclusure at 250W amp. it's alright but i think it could be better. would 2pcs of 12" subs with the same 250w amp make a big difference? i really don't know which one is better?! anyway, i'm also considering the space that it would take for 2 12" subs. my current enclosure i think has 1.5 cubic ft. i think 2 12" subs would have a bigger box. but by how much? i wanna be able to get the spare tire just in case. hope someone can enlighten me. thanks!