Good Subwoofer recommendations


I'm looking for a good Sub for my existing HT system.

There are so many types like Sealed, Ported, Cylinder, Bass-reflex, etc. & it's a bit confusing to determine which one will be better. Also, does type of speakers or Amps I have can impact the decision?

My budget is around $1000 & I prefer getting a used or refurbished rather than new.

Current setup:
LRC Speakers: Tyler Acoustics Linbrook System II
Surround Speakers: JBL S312
Amplifier: Parasound Halo A51
BD Player (cum PreAmp): Oppo BDP-105
Room: 16x18+ with ~40% open walls, so sound can bleed

Thank you in advance!
hitsofmisses
Rhythmik and REL make very good subs, as do SVS. However, my favorite subs are the Velodyne DD and Optimum series - these are *fantastic* subs...

http://velodyne.com/subwoofers.html

-RW-
There is a Vandersteen V2w here for $950 that would be my choice. I have the audio-only version (2Wq) which has been a terrific performer--fast, tuneful and integrates well with the speakers.

PSA xs15se 15 inch sealed down fire, excellent for ht and music. I think they are about 750 brand new and delivered.
I had Tyler custom-fabricate a really nice subwoofer for me two years ago. Fits the bill perfectly, and the finish matches my Woodmeres.
Is sub primarily going to be for music or HT? if for music I go with REL and not look back. REL is tight, fast and musical. good with HT but not great, unless you go with their higher offerings. I just ordered two REL t9's which houses two 10inch drivers and should fit the bill for my room and should do pretty well with HT.