Even if you did use a true infinite baffle subwoofer in the kick board, the kick board is thin HDPE and not nearly rigid enough to support a woofer (not from a structural but from an acoustic standpoint). A compliant baffle panel will waste alot of bass energy and is one of the primary reasons for bad infinite baffle execution and reputation. The other major problem is that the kick board is wide open over the top so you will not have front to rear acoustic isolation. This results in compromised bass extension and compromised power handling, not to mention terrible sound quality.
My recommendation would be to do it right or not at all. You really don't want to be stuck with a useless hole in the kick board after you discover that its a total disappointment.
I'm not discriminating against cheap or entry level. I love inexpensive. But once you cross the threshold into wasting your money then I have issue with it.
Here is what to do if you insist on doing it "bass on a budget". Get an inexpensive small box 10-inch woofer from Polk, Alpine, Kicker, etc, as long as its a credible name brand. Get a small sealed automotive box. Make certain that it has more than a press-in terminal cup. Screw type only! Elevate the box up off the sole by a 1/2-inch or more with polymer mounting pads. If its not a marinized box, the MDF construction and hot-glued seams won't last in a boat but it might get you through one season until you can get a real enclosure. Note that carpet will cover the failed seams long after the damage occurs. But change it out before you ruin the woofer as the suspension will prematurely fatique in a faulty enclosure. Again, one season only and you will be on borrowed time at that. Direct the sub at the exterior starboard hull surface so that you benefit from a lttle boundary loading affect. This will get you a small gain.
Like the sub, get a good name brand amplifier. Don't get sucked into the outrageous power claims. If it says 1000 watts for $200, it just isn't so. Go quality over spectacular specs. The sub is only as good as the supply. So, be sure to get a good gauge of primary wire and thicker gauge terminations.
That's the short list. If the unexpected costs are mounting and you feel compelled to make compromises to just get it done now...don't do it. Put it off.