if you have a correctly built box, correctly ported if that applies, good wiring, an adequate amp, gains set correctly, coil(s) hooked up correctly, a good headunit pushing, and a quality battery pushing, you should be more than fine with (2) twelve's, especially in a truck where the audio is at most 2 feet behind you.
now in say a car where the noise has to travel through the trunk, rear seats, and then to your ears... i can see having a 15 maybe...
but honestly, like steve meade and people like him... they are just people with too much money and time on their hands... it's pretty much pointless, and they will most likely encounter hearing problems in the future... so have fun with that!
that being said, if i could have steve meade's cars/trucks for free, I would take them, and drive them, and show them off with no questions asked... but i would never spend that much money on 8 15's and such... it's just a waste to me. and a health hazard... not to mention against the law, pretty sure a cop would pull you over for disturbing the peace, ESPECIALLY at night.