im usally listen to rock or rap i dont know how much im expecting to pay i guess as much as it cost to have a nice system.
my air space i guess i would have to guess like the trunk is 3ft by 4 or 4.5 ft
and whats spl?
well this is the deal, if you listen to rock and rap i would suggest that you buy subs to accommodate a median of Sound Quality and SPL. This isnt that hard to do since now-a-days there are a lot of well-rounded subs that play good at both levels.
I would reccommend. . . Alpine Type R's, Adire Shivas, Infinity Perfects, Soundstream Exacts (if you can get ahold of any), MMATS Pro Series, or IDMAX's (if its within your budget.)
If you have 4 feet of trunk space it sounds like you have alot of room to work with... if your not worried about space then you may like the Shivas, or MMATTS Pro Series
If you want to save room then go with the Type R's, Infinity Perfects etc..
SPL Stands for Sound Pressure Level. . . basically this is what BOOMY cars have.
SQ (Sound Quality) is more of a crisp cleaner bass, but dont normally hit as hard as SPL numbers.
After you find what subs you want to go with you can start from there and start shopping amps, mids, highs and so on.