Sealed subs are Usually recomended for High end SQ setups because they work well over a wider range of frequencys. In ported set-ups, the port is tuned for a particular rang of frequencies, therefor U'r sound quality, and/or loudness will decress outside of that frequency range. It is possible to tune the port perfectly, but it usually takes many trial & error for that particular car, box & sub.ofcourse U wanna use a high SQ sub (I would go with 2 - 10" 's) . I've always liked Crossfire & Diamond Audio, but there are many great sounding subs out there , many are listed daily on this forum, those are just two of my favorites, I have note have the privlege to test some of the others commonly listed on this furom in the exact same conditions as I have these. Crossfire is an excellent SQ sub though. If U go with a ported sub, U will basically be doing it to go louder (but U will be loosing space that U could use for anouther sub. Two 10's sealed will leave room in U'r trunk than two 10's ported. and 1 10" ported will not sound as good in terms of SQ as 2 10's sealed.