Bench sub box

I have a sub box under the back bench seat in my 02 avalanche. I am not satisfied with sound this box creates. it just doesnt seem to hit as hard as the potential I know my subs have, (2 10" infinity reference series subs). Any suggrstions for improvement?

What is the shape and volume of the box the speakers are in? Homemade or storebought (brand/model?) How is it mounted and speaker orientation?

Offhand, it sounds to me like the enclosure is too small for the speakers and is probably sealed and not ported. The speakers have to work against the air pressure in the box (and each other) to achieve any real movement, limiting their response. You might try a larger enclosure or go to a ported setup. But give me some more specifics to help understand your installation.