Ported or Sealed?

not a problem

It really depends what u r looking for, if u after big bass and SPL def go ported, but this might be a bit peaky. A sealed box will solve this problem and give u a much flatter response, these are great for SQ. If u do decide to go ported dont worry about subs nuking themselfs below tuining freq. This will only happen if u do it reapedly and one solution to overcome this is to tune the box really low ~25Hz, and if the amp comes with a sub sonic filter just set it to the same level (25hz). As u have a sedan u might want to see if u can port thru the parcel shelf alowing more bass into the cabin of the car, if not try to rear load the subs towards teh boot lid. This will also give an increased output in both sealed and ported configerations, at teh cost of a little bit of a boomy sounding bass.

I would go sealed based purly on the fact that it provides much flatter response and can still put out some reasonable SPL numbers in a largish box.....