It all depends on what kind of car you have( size wise per say ) which way the subwoofer is facing, and what quality subwoofer it is. I sold my old subs to my friend and they sucked so bad in my car, and then we put them in his 2 door grand am, and they sound ba, so in reality, what might sound great in mine, might sound like crap in yours, the single l7 might be loud, but it all depends if the trunk is sealed, and what kind of music you listen to, if you listen to rock and metal, go with a sealed box, the smaller the quicker the sub can keep up with the drums, but if you like rap or more electrical music, go with the ported for the low lows. its all based on your car type and sound preferance. My single ported 555 is way way way louder and cleaner then my old 12's ported with out a doubt.