This is my current situation. I would like to upgrade my universal slot ported box that i bought from future shop (it doesnt hit lows that well as my previous 12" sub but has much better punchy bass) to a custom made box. My current sub that i would like to build the box to is a MTX MXS1204, i was planning on building the box size MTX recommends in there manual here: http://www.mtx.com/caraudio/products/manualsQuickInstall/subs/TechData_MXS1204.pdf

The amp that is running it is a MTX TC4002, i am running it bridged in a 4ohm, I listen to a range of music from punchy bass(metal), to low constant bass like 36 mafia late night tip(sorry not to sure of the correct spelling.)

I have searched the help about box tunning but still am cluless about all that stuff and such. I would like to achieve a sound that will sound good over all types of music but still retain SPL. Would i notice a notable gain in bass for building a sub to spec?? I am aware that box design is very important, but i have no idea how to match the sub to a box or even the car. So if you guys have any insight could you help me out with a design for this sub please??
BTW if you guys recommend a 2.25 cu3ft box how would i calculate the rest of the measurments such as the port size and stuff...

Thanks for all the info guys.....

Josh