Back to the post and the answer to the thread starters question. The answer to your question of "why does it sound like crap and does not get off" is NOT because it's a prefab box. I prefab boxes that are common sales for me, such as extended cab pickups. The problem is that your particular "prefab" is of small volume and is sealed. If a pair of 10's won't get off in an extended cab pickup, one the box is not vented and/or the enclosure is roach d!ck tiny! You don't get big sound from a small sealed enclosure, you are limited to the displacement of the cone x it's stroke capability. That's the least efficient thing I can think of other than just sitting a sub bare azz nekkit in the back seat and expecting it to get loud. The fastest, least expensive cure is to take one of your subs out, knock the center divider out of the box, replace that with a center brace that allows plenty of air to move through and cap the hole of the removed subwoofer. Next is to vent that cap to the tune of 16 square inches of port area per NET cubic foot of enclosure volume. Make that port 16" long and you'll get louder on less power, guaranteed. If you want to stop playing around, lift the rear seat 3" with 2x3" square steel tubing and some high grade bolts/nuts and washers. Then you have room for about 2.5^ft of net volume under the seat after subs and port. Built that box with a center vent that is rear firing and is about 3" from the back wall of the cabin. Now your truck will get stupid. The vent needs to be the same formula... 16 square inches of port area per NET cubic foot of enclosure volume x 16" in length. You will be happier either way you go, just way more so with the latter option. Have fun with it and get back with us when you opt for a louder solution.