Got rid of my subthump stealth box and replaced it with a 1.2 cbft ported box tuned to 32HZ. The stealth wasn't cutting it. The box was built by a local caraudio.com forum member. Very pleased with the results.
i have a dual 12 subthump box with 2 new model memphis pr's geting 600rms from me memphis belle 1300 and it sounds good but before that i had a memphis m3 in a memphis ported box about the size of yours and that thing rocked.
i sold it to a friend who but it in his tahoe with a 500w xstant amp and i cant imangine it being any louder lol.