they **** actually.......average sub worth about 100.00 in an average plastic box worth about 150.00...... If your looking for something for your silverado I would look at something made of 3/4" MDF wood and find the proper sub for its reccomended size........
There are plenty of decent little specialty companys that make vehicle specific enclosures or you can have one custom made like I did
by Woodlawn
Actually, from what I hear, the JL-built enclosures, while very pricey, are still pretty good. I haven't heard anything about this specific ones, but the Pro- and HO-wedges sound good from what I've heard. Plus, the 10w6 that comes in the one he posted is no slouch.
It comes down to a couple of things.
1) Do you absolutely NEED the box to be countoured to every little hump? With as much space as there is under those seats, it shouldn't be hard to make a regular angled mdf box to fit underneath. It may not be a "custom" fit exactly, but as long as you match the carpet, it should look good enough.
2) If you decide you want the custom-fit, can you get a fiberglass box built by a shop for less money? If so, or you can find a good non-loaded custom enclosure on the net, you may want to go that route instead. As long as you can get the enclosure for $450 or less, you have a wide range of good subs to choose from.
Personally, I'd just buy a couple good 8s and build an mdf enclosure for under the seats. Figure max price on the subs would be around $400 (rl-i 8s). Sheet of mdf is ~30. That leaves $270 left for amp/wiring/whatever before you hit the price of the JL unit.