I feel you need a sub for a good set up. i recomend a 10" as they are the best compramise between the 12" deep range and the 8" responce. you could also do 1 8" under each seat.
as for the pic it is a competition truck and it is a truck so there is no space to work with what looks like 4 12". it looks like a SPL job. not my type but it is varry good.... in a way.
you will see a lot of wierd things with spl http://www.mecacaraudio.com/