Can anyone help me build a box for 2 subs?

[brafferty]

ok here is another question that's entered my mind, maybe a downward firing sealed box? I've heard that it is a nice set up but I've also heard that the cones begin to sag EVENTUALLY? if i need to i can maybe post i link to a mix of the types of music i listen to, i want it loud since im competing with a 1000 watt dual ported system, but i want good quality as well, and they just seem easier to build first time around. Thanks for the input in advanced