as i was saying, headlights aren't dimming from the box, headlights are dimming from your wiring..
Build a new box, use 3/4" MDF, not particle board, not chip board, not raw wood(wtf is that?). This time go ported, give that 12 about 2 cubes and tune it between 30 and 35 hz use toores calculator to figure this stuff out or ask for a design from someone else. And get that wiring upgraded. Use 4 gauge wire for both the positive and negative, ground the amp to a sanded off (bare) spot of the car, or better yet the frame. Do the big 3 under the hood. You'll notice an increase in sound.
Edit: and stop swearing by overpriced, buying the name only, brands like JL and RF. For the price you paid for that sub and amp, you coulda bought 3 times the wattage, and a sub with twice (or more) motor force.