nice job, personally i would have built a box that would fit under the STB with the subs facing the rear, the reason for the subs facing the back is cause the sound waves will have something to ounce off of. right now they are hitting the back of the seat and coming back at the box( if the seats up) and then all your wires coud have gone under the carpet and out where the seats split, that would make the back look clean.
having the subs facing the other way would let the sound waves hit off the back of the car and then go directly into the cabin .