Xplod is junk. Save up just a little bit more and get a better quality system.
Some examples...

Sub: Diamond Audio 12" CM3 (~$109), Kicker 12" Comp VR (~$99), Alpine 12" Type S ($109)
Amp: MTX Thunder 251D (~$129), Kicker 04KX200.2 (~135), Alpine MRP-M200 (~$139)
Walmart 4ga wiring kit ($25) or 8ga wiring kit ($20)
And for the enclosure, just build your own out of MDF or get a cheap prefab built to good specs.

Keep in mind that the amp and sub prices are off of onlinecarstereo.com and you could probably find cheaper prices on Ebay or locally. This would leave you with a way better system than any Xplod "system" from Good Guys. My buddy is a manager at Good Guys and when people want to buy Xplod, he'll suggest a ton of other brands before caving in and recommending the Xplods.