Look through the threads around.
Throw up a few things here - one, the power. Once you start getting to 1500 RMS watts, you'll need power upgrades, and that'll cost you a nice chunk. So, if your on a budget, stay probably at at least 1200 RMS or lower, or you'll stretch the power. You'll want to do the Big 3 wire upgrade, search on the forum for that, too.
Second, you can build a much better box, for much cheaper, that will sound better. Look around and find someone here who can design a box, and you can get the sheets of MDF at Home Depot, have them cut it, and you can put it together. Get some good conductive bolts for the connections, just a few extra dollars.
Third, the MTX subs are not very good. Especially for the price. The L5's will be fairly loud, but you can do much much better for the price. Look at subs such as the RE Audio, FI Audio, and other, not so known brands. ESPECIALLY if you're looking at something that will sound good. Honestly, those MTX/Kicker subs will sound like shit, especially in a prefab box. Building your own box will make a huge difference.