[AceX]

A ported box for those types of subs often hurts more than it helps...

If you want it to hit harder, add another sub and an EQ to adjust the system. You can make them hit harder by adjusting crossover points, slopes, and gain.

Adding another 10" sub just like the one you have should do alot to solve the problem, but might create the problem of not having good enough mids/highs.

I say add the extra sub and go from there. It's the cheapest and easiest solution. Just beware that more isn't always better. I have more than just about anyone and I've spent I can't tell how many hours tuning, and still have many more to go...