Musical Subwoofer for 2-channel system

I am looking augment bass to my 2-channel system. My system consists of:

Bryston 3BSST Power Amplifier (170W RMS/channel)
VTL 2.5 Pre-amplifier
Cambridge Audio 840C V2 CD Player
Custom 2-Way Monitors with Accuton Ceramic Drivers

I am looking for a musical subwoofer around $700. My room is 15x15x10 (LxWxH).
Will a passive subwoofer like the SVS Passive Cylinder 25-31 CS–Plus do a decent job? I am also open to active subs.
I would try and up your budge to $2k, and look into a REL B3 for a truly musical sub.
At $700 you are in the Vandersteen 2Wq range, they are know to be very musical definitely worth checking out.
Based on my experience with three different subwoofers from them, I recommend you listen to Mirage before you buy anything. Their subs are musical first and foremost, and are easy to blend. Furthermore, with the room size you have, you want a small one.

I specifically recommend the Mirage Prestige 8 sub. 8" driver in a 12" cube. Crossover adjustable from 40 to 120 Hz. Linear down into the 20s. Uses an 8" fiberglass composite cone with elliptical surround, very similar to the bass drivers in their $7500/pair flagship OMD-28 full-range speakers. Price of the Prestige 8 is smack dab in your price range at $579. For deeper bass and more output, move up to the Prestige 10 at $750.

I can tell you, those elliptical surrounds WORK! They allow the driver to make bigger excursions and stay linear, getting more articulate, deeper bass than you would otherwise get for a given size, loading, and power. I have a pair of their OMD-15 floorstanders, and with those elliptical surrounds, the bass quality and quantity produced by their 5.5" drivers is a big surprise. You really hear what *kind* of bass you're listening to, be it mic'd acoustic, contact pickup acoustic, electric, flatwound or roundwound strings, which pickup was selected, etc.
Lets throw in there the MJ Acoustic subwoofers. I currently use there 100 MKII in my living room with seamless integration thanks to it wireless remote. Plus it has a variable phase adjustment making set-up more of a breeze. The most musical sub IMO under a grand.
A used Rel Strata fits your criteria: very musical, easily blended and low and high inputs.
I've narrowed my search to either 2 JL Audio F113 Fathoms or two Velodyne DD 18s. I still haven't decided. Can anyone offer some help?

I excited about the JL Audio for all the great press I've seen lately. I've noticed it is used in several members systems.

The Velodyne's setup routine sounds like it is superior to all others.

The Velodynes' also has a servo mechanism, I'm wondering how effective it is and if this makes it superior to all other subs?

Again I will only be using this in a two channel system for music only.
Please help me decide.
It would be great if anyone knows how to contact Larry Greenhill from Stereophile? He has reviewed and reportedly owned both subs, so I'd love for him to respond.

Sgr, You can probably post a note to Larry over at Stereophile's forums about his subwoofer review in the last issue. If you've read that review, then you'd probably also consider the SVS PB13-Ultra. You can pick up a pair along with a Velodyne SMS-1 and have a good deal of money left over.

Velodyne DD18
JL Audio Fathom F113
SVS PB13-Ultra

You can see that the SVS sub plays cleaner than the others.
Bssk, your $700 will get you the SVS SB12-Plus. It's a sealed design, will let you run balanced cables and provide the necessary crossover to high-pass your 2-way monitors. Note that it's a small box so it's performance isn't as good as their larger subs like the $600 SVS PB12-NSD.
A Velodyne SPL series sub will blow away any SVS for music. SVS shines for home theater though.
There is a James EMB 1000 sub for 750.00 on the GON right now, I've heard good things about them, but have never heard them myself. Maybe someone who has can comment.
A Velodyne SPL series sub will blow away any SVS for music.
Velodyne makes good products. David Hall has always been concerned about distortion. But why do you think your statement is true?

SPL 1500R

Yes, it's quite clean for music -- >30Hz and <105dB. Of course, so are SVS subs.

When you consider the demands that music places on a sub many "lesser" subs are quite adequate. They don't have to play as loud or as low as in a HT situation.