I am trying to decide whether I should build a new ported box or keep my subwoofer in the sealed enclosure it is in right now. It sounds like using a ported box is more complicated than just building it because I heard that if I don't set my cross overs and stuff right that I could ruin the subwoofer. Is that right? And I was also wondering what are the negatives to using a sealed enclosure versus building a ported box? I mean, do sealed enclosures lower sq or spl or anything like that?

1) yes porting is more involved, but not prohibitively so
2)You need to set crossovers correctly for ported and sealed designs
3) you need to build the ported box correctly to put the peak at the correct point to either maximize SQ or maximize SPL
4) a sealed enclosure will always have a lower SPL than a properly built ported box
5) a sealed enclosure is usually smaller than a ported box, sometimes quite a bit smaller
6) Ported designs tend to have a dynamic advantage
7) sealed designs can take more power safely
8) for SQ sealed is easier

1) yes porting is more involved, but not prohibitively so and ported is way better so it's worth it.
2)You need to set crossovers correctly for ported and sealed designs but ported is better.
3) you need to build the ported box correctly to put the peak at the correct point to either maximize SQ or maximize SPL which is one reason ported is so much better - it is flexible.
4) a sealed enclosure will always have a lower SPL than a properly built ported box because ported boxes rule
5) a sealed enclosure is usually smaller than a ported box, sometimes quite a bit smaller but it's worth the extra space to have a ported box
6) Ported designs tend to have a dynamic advantage because they kick ass
7) sealed designs can take more power safely but it you have at least 3 brain cells this is a non issue
8) for SQ sealed is easier but ported is worth the effort

4) a sealed enclosure will always have a lower SPL than a properly built ported box