That is a stereo amplifier, it has only 2 channels, one for left and one for right. What I would do is to get a subwoofer in the trunk, and one more mone amp, or an active sub (built-in amp). (If your head unit has a sub output). And run the amp you have on the 6x9's and the kick panel speakers and dash speaker like Bullitt suggests. You can run the 6x9's as subs, but those are so nice to have fullrange in stereo.