I feel ashamed for the guy with the sub in the first link. If you're going to do a wheel well sub, learn to fiberglass. That set up is so....Bad... And the grill... :nervous: Thats scary and looks sloppy, at least to me.
If you are going to lay down carpet over your sub, don't use the car carpet. I saw some guy on ICIX forums that did a wheel well sub. What he did was mounted the car carpet onto a board and cut out a hole where it would cover the subwoofer. He then took some speaker fabric, the same color as his carpet and mounted it over a flat grill covering the subwoofer. The cover could be removed if he wanted to show off the goods. It looked really clean and he could still put things over the subwoofer without worrying. It also sounded well, as he said.
By putting car carpet over the sub it will sound nasty and muffled because the carpet is thick and doesn't breathe at all.