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
Check out SVS. They are a great company. 45 day return policy with free shipping. I had the SB-1000 and it was outstanding.
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.