youd be surprised what soem good bracing would do for you //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif .. and maybe a couple extra baffles on the front side too.
unless youre doing something besides a normal sub box i guess.....
go to your local lumber yard.... but expect to pay a crap load //content.invisioncic.com/y282845/emoticons/greedy.gif.5a53e6246569d7ab79867170f3b06629.gif