yes, you definitely want to bridge the amp.. bridging will unleash more power from your amps, and also, won't separate the right bass signals with the left...
erm, about converting a sealed to a ported enclosure.. sure, it's possible if you're really good with wood... but even so, with all that trouble, it might be better to build yourself a new one...
a ported box will require more space, and the port itself will take some volume, while you've got to maxmize it...
FOr exact volume and port length + diameter, you'll need to specify what subs and what kind of music you listen to...
ported boxes can be tuned to peak at a chosen frequency... hiphop is not as low as you might think... about 40~45Hz is where most rap bass hit...
test tunes will test your subs to the limit with their 20Hz, but it's inaudible and you're required subsonic filter would've cut that off...
port tuned to 30Hz doesn't mean it'll peak at 30Hz, it will peak at a slightly higher Hz, maybe +5~10Hz more, depending on the size of your box.
