The only box I have found made specifically for the 2007 is here- http://www.supercrewsound.com/shop/detail/11/59.htm (only single 8" or 10"). Also, I believe MTX makes a Thunderform for the '07.
This weekend I'm installing this box (http://www.crutchfield.com/S-OrznWi9f7xw/cgi-bin/ProdView.asp?g=178650&I=130SBOX10U) with the recommended Pioneer sub and 210 Watt Kicker Amp. I'll post with my results.
tguno, you probably won't find one made for the ST. Most are made by someone that owns a ST or knows a costom shop that can do it. I really doubt you will find one prefab'ed. Especially if you are looking to put 12's in. There are some on here that took the back seat out, built the box, secured it to the floor, then secured the seat (without the seat hardware) to the box. I'm not sure if you'd get the "airspace" needed to run 2 12's with a box that will go under the seat with the seat's hardware still under it.