erm, yeah ported would be better, and tune the box to about 35Hz for low bass, or 40-45Hz for SPL. A ported box will never play lower than sealed, but it will be louder/more efficient at the tuned frequency, so it will have a louder feel to it with your genre of music. With rap, you'll most likely never notice the downsides to a vented box, like coloration from harmonics, or the sharper roll-off below the tuned frequency.