12's are REALLY tough to fit back there because of the height. If you are looking for a stealth box, let me know. I have a friend looking to get rid of one. Also, the amp you have might not be what you need. The higher the power, the better the damping effect it has on the speakers. Basically it controls the motion of it better, thus giving you a tighter, cleaner sound. I have a 300X2 running my two 12's in the trunk, and I'd like to go higher. I don't want it any louder, I jsut want a tighter sound. Oh, I went to school for recording, so I've studied amplifiers and speakers pretty extensively, so I know the inner workings and physics of them quite well... Just letting you know I'm not talking out of my ass...