I saw a guy one night that had 2 type R 12"s in a ported box powered by 2 MRD-M1001 mono amps. Im not exactly sure of the ohm and all that, but it was pretty much the hardest hitting car ive ever sat in in my life, bout made me sick, and it was clean and crisp sound to. His setup is what made me get the setup I have, except im only running 1 MRD-M1001 instead of 2. His box was the exact same as the box i have also. I would go for the 2 12's in the ported box with the 2 mono amps for the best sound and hardest punch. The 15 is going to be a bit louder because it will be more efficient, but i dont think it will be as smooth and crisp as the 2 12's. I guess its just loudness on the low tones with the 15 verses Harder hitting, crisper bass with the 12's. I have a friend with the 15 running off of a an old punch 1000, and it pounds pretty hard, but again, its not nearly as clean, just obnoxious. Hope some of that helped, if not, well ill try harder next time.