Hey, I speak from experiance when I say this, but I will never again build a box out of regular old wood. I built one in high school wood shop cuz I had nothing better to do. That was the worst sounding hunk of garbage. MDF is the way to go. You'll definately need not only bracing, but also get some packing foam. I can't remember the exact name of it, but it's kinda like the stuff they fill pillows with now a days. I used that in the box I built and it helped out a ton. Look around for it. Your local sound shop should know more about it.
'05 Base Coupe, Blue, 2.2L, 5 speed manual, Too many mods to list in this signature. I'll just say insanely loud system, fully upgraded suspension (nothing original), Intake, Full Exhaust from the engine back, Rims, Tires, etc... Give me about a month to get back stateside and pics will be posted in the vBGarage.