You have PLENTY of room to build a killer system in the ex cab section if you wall it... I know a guy that has 4- 15" T1's in his S10 Excab and that thing crazy.
Here's my setup, not in a mazda but a bagged TBird. Im still working on it but our Mazda build has kept me from working on it.
I also have a SA12 on a T1000.1bd in my grand Cherokee tuned @30hz and it beats the block down, it's not really picture worthy though.