If it was me i would go with a single 12 over a pair of tens. it will be a lot cheaper, go in a smaller box, and able to produce the really low stuff.
Honestly it sounds like you are really a candidate for a sealed box, but i have built a lot of ported boxes and they can be just as good sounding as a sealed.
What would i recommend
Alumapro Alchemy- great for natural sounding bass this is just a great sounding sub period, not made for getting super loud, but the aluminum cone and magnet structure are very classy for a show install... can't go wrong with this one.
IDQ- nice tight low hitting sub- great all round sub,
Adire Shiva- The best of everything... sounds awesome, cheap, loud, efficient as hell and hits deeper than just about anything you can imagine.
Adire Brahma- this sub is expensive, but it just blew me away, i have 400 watts on it and it gets pretty loud but it sounds better than just about anything i have ever heard, maybe even better than the IDSPL that i used to have... only more listening will tell. If you have $380 for a sub i can think of NO better way to spend the money!!!
Boston Pro- For the ultimate in a super tight bass this sub can really deliver, while there is better combinations of SPL and SQ subs out there, this one is severely lopsided to the SQ side.
Eclipse Aluminium- Very nice and buttery smooth sub it has great sound quality, but it is not really that efficient and it is fairly expensive, the aluminum cone is also VERY classy and if you are into a show system this is a great sub to consider.
What would i not recommend
RF HX2- gets pretty loud, sounds OK but if SQ is is the main priority get something else
Kicker L7- Expensive, LOUD and sound like ass, if you want a sub for getting loud get this, if you want a great sounding sub put this next to the RF HX2 and the HX2 will sound as good as a Velodyne, put it next to a good SQ sub and you realize that it really is that bad sounding.