BlackCrossFire6spd,
If you need extra 'space' in the passenger footwell area... go with a smaller AMP and remove the factory one... takes a LOT of space under there and there is also a lot of open space behind it.
To build a box with a built in AMP and sub that fit UNDER the carpet would be the ultimate stealth install in my opinion.
I have plenty of bass for my nearly 40 year old ears... but others like that 'shake you fillings loose' feeling.