Subwoofer for Beginner

I bought a Sony SA-W3000 at Fry's for about $100 (open box).
It's not Audiophile quality but has a powered 12-inch
woofer and will give you more than a taste of what
Bass reinforcement will do for your sound.
I use it for Home Theater.
I use a B&W ASW650 in my "Big Rig" and it works fine.
The trick with subwoofers is to use volume sparingly.

Finally, I've asked Santa to bring me a pair of
Velodyne DD-12 + in black piano finish.
Yep, that'll do it...

Dhcod, you have a very nice system. Buy a sub which is built for music, not home theater. I went with a cheap model a few years ago just to see what a sub could do for my system and the end result was that all the detail in the bass was lost, the sound was no longer musical.
I think you need to be in the $600+ range like the SB-12NSD or a used REL or Velodyne.

Rythmik subs available through Ascend Acoustics provide phenomenal bang for the buck.

There was an Audio Asylum member and speaker builder who built a subwoofer using a Home Depot plastic bucket (NO kidding!) and a Parts Express driver. According to all who heard it, it was pretty darn good. The build was easy to do and the cost was very nominal, less than $100. I think this is a the way I'd go if I were you.

Here is the link:
http://thehornshoppeforum.com/index.php?topic=406.0

-RW-

HSU Research specializes in subs and has good return policies/user support. The VTF-1 Mk2 is very musical, well reviewed and on special direct from site for $419.