Be careful with budget ported subs. They might give you output but if you can not turn it up pass half way because it sounds boomy and distracting then what's the use if you aren't utilizing the output. Look for a good sounding sub first of all and utilize whatever output you can get out of it. Sealed aren't whisper quiet and do jam, it just ported get little louder and lower usually which is better for HT but they still need to sound clean.
There are a lot of good subs so select wisely or you might end up not totally happy with your pick. One PL-200 is ported and Loud (for the price) so you might only need one but only decent where SQ is concerned. Emotiva Ultra 12/10 for sealed is supposed to have good SQ with good output. HSU and Epik make great subs too as well as the Outlaw and few others that are still good value. Check reviews on this site and over at Audioholics to get a better feel.http://www.audioholics.com/reviews/s...rs/allContents
Nothing wrong with starting with one good sub and adding the other later on if you want better balance or more output.
Sometimes ported is not like getting a Corolla when you want a Camry but getting a truck or a van instead. Just don't want you to make the same mistakes many made, including this poster, when getting a sub.