I currently have an HSU VTF-2 that is great sub, but I wanted a sealed design for music only. So I bought the Titanic MK3 12" (295-404) and the 500wt. plate amp (300-404)from Parts Express.
I then built a 2.4ft^3 cab out of 1" MDF, finished it in a adhesive backed Teak veneer, high gloss laquer, and it is a beaut.
The sound is very tight and quick, the F3 point is 28Hz. and the F10 is around 20. It keeps up quite nicely with the HSU, and the amp has a built in Parametric EQ. to tame those wierd room problems. Plus you can say "I built it"
Adire Audio also has some great products.
Whatever your decision, good luck.