It really depends on the sub. I have had different results with different subs, It also depends on the tuning of the box, the most common problem I would say with ported boxes is a humming sound when it hits certain higher notes. Tell ya what, Call up sundown and tell them your sub/amp and music preference and see what box they recommend.
For example I partially bought my sub to go in a sealed box, the specs show that it can be used so I went with it. When I was done I called RE's tech support and he strongly recommended me trying a ported box. He said while they show their subs can run sealed, they are meant for ported applications.
As far as the ported for rap, sealed for rock debate. It really comes down the the subwoofer, that sundown should be a great sub. I would expect good sound quality from it in a ported application.
I am running mine in a 1.0 cu.ft. after displacements ported box tuned to 34hz. For me thats a little high, my next box will be tuned to 31hz. But all in all I am extremely surprised how it sounds in a ported box. I listen to a variety of music. Rap, Country, Old rock, New rock, and some in between stuff as well, so I needed something versatile. This does it for me.
I started off wanting a simple 10" kicker CVR in a console powered by a zx400.1 that I already had, but quickly spiraled outta control! The components alone are twice as much as I intended to spend on the whole setup.
