I mean that should not be too hard if you set it up correctly, I bet money you could get louder with 2 dd3500's and 4000 watts or so.. hell even 3000 like him. I mean the mt's arent going to be much good to you if your only putting 1500 watts to each, you'd be better off getting some more efficent woofers. There are many possibilities, but also what is your brothers box tuned at, and do you want to be louder to the ear or on the meter. IMO I would rather be just as loud and sound good while doing it, but I am werid and I think the dd's 9500 series sound good. I heard a mag on rock music and it was really nice, but I don't listen to rock, so I would not say I am not the person to ask when it comes to SQ (too you, not to a judge they know what subs should do and how to judge they're sq) but I heard some mt's and they did sound like one note wonders... Even if you listen to rap I think you would be better off with more effiecent "sql" style woofers with that kinda power... Really you should try and meet up with people that run all these woofers like re's dd's si's and everything else, see what they are running and how you like the sound and they pick what you like. Everyones different, I had a avalanche which is a pretty highly reguarded sq woofer, and I liked my destroyer more and the 9515 even more in sound... Its all personal preference, but I really think you will see how the mt's sound like "one note wonders". Even though XBL 2 subs like the xxx's and avalanches are very accurate some people don't care for the way they sound. That's why I say you go hear all of these subs set up right before you make your mind up based off of what you hear on the internet...
I also think people should focus more on front stage and eqing before they go out and get woofers, and focus on the SQ of the subs, while they run stock front stages....//content.invisioncic.com/y282845/emoticons/*******.gif.a649d21efc0d1fd4890a6428166586c1.gif