Holy shit that box is not ok. You need room for the port to breathe and as has been said idk if you have room for 2 12's. I wouldn't be surprised if the bottom subs were partially working as PR's in that box. Rebuild a new box wood is cheap bro. Get someone to design you a proper enclosure.
The amp probably does 2.4-2.5k on a good power supply if you even have one. Be careful because I can bet you that if that amp clips it will overheat faster than you can say shit.
P.S. when you're at lowes tip the guy cutting your wood so he does a good job.