digital designs subs

Hi, I have a question i own a 1999 gmc yukon and im running 4 12" kicker solo baric l5's off a hifonics colossus xx 3200 watts rms (1600 x 2 at 1 ohm) or 3200 x 1 at 2ohm ) i have all the subs and ports firing upward and i can smell the voice coils heating up i back the gain off a lil and then it doesnt sound that loud for 4 12" and 3200 watts. So my question is if i buy 4 12" digital designs modle 2512 and fire them backward along with port will i notice a huge increase in how lud it is in the truck?? wondering if anyone knows about theese subs and could let me know what the results may be. I want it to be very loud almost to the point u cant sit in the truck with it playing. if anyone could help me out i would greatly appericate it