sub box, 2000 chevy extended cab

I have a crew cab with 4 12" alpin type r's and had the exact same problem - it sounded like garbage even with 3000 watts. I had a center port with the

subs around it like in the picture. It sounded best pointed up but still not very good.

My next box I built had the 4 12's along the bottom with 2 areo ports like the picture below

This box sounded much better than the last and sounded best pointed foward. The size was about 9cu.ft. net. I later shrunk it down to 7cu.ft. net, it lost some low end but picked up the high bass alot better.

I think what I would do if I was you is to build a box with the subs foward and one long port along the back top of the box. It may not follow the 7 to 1 rule with port dimensions but i've seen and heard it before and it sounded good. I would divide the box into 2 chambers, so 2 ports along the top back of the box.