Cost Effective Sub Woofer

Interested in obtaining a cost effective sub woofer for a reasonably good sounding two (2) channel stereo system consisting of the following equipment: Monitor Audio Gold 100 speakers on monitor Audio stands, Rotel Integrated amp, Linn Basik turntable with Rega Exacta 2 Cartridge, Kimber Speaker Cables and jumpers, Interconnects and digital cable, Marantz 5004 CD player, PS audio Power Cords. The music room is not treated and 17 x 24 in size.  Any suggestion on a sub woofer. Prefer to stay under $1000.00. Listening preference is jazz at moderate volume. Not loud at all. 
For brand new - sealed servo Rhythmik F12. It's right at that price point.
Look at REL, seemless integration and it will be perfect for your monitor audio gold 100 and your listening preferences.
A little out of your "preferred" range at $1299, but it has so much going for it (Anthem room correction, plenty of power and it has wireless capability) I think it’s a sound investment (pun intended).
Two SVS1000sb can be had for $950 for the pair direct from their website.
joscow, read up on the subject, you will find the benefit of using 3 or 4 subs so outweighs the choice of sub that four dirt cheap subs will be much more cost-effective/high performance than the same amount spent on any single sub - no matter how much "better" it is.
HSU makes a wide variety of subs.
Perhaps not the 'best', but they are quite good and do what they are supposed to do, and the price is right.
Dang, I think we covered everything except used Vandy 2wqs. Great job team!
Joscow, you have a very large room. One sub is going to get lost. Save for longer and get two identical subs. The best value is a Parts Express kit. Two of the 12"subs would be fine. The drivers are seriously good. 
I use (and recommend) Rhythmik, but a pair of SVS sealed 12” subs can be had for just under $1k. You’ll get smoother response with a properly situated pair of subs than you will with one. The 2 x 12” drivers will play very loud with low distortion and the sealed enclosure ensures tight bass. They’ll play as low as 99.9%+ of all recorded music program material demands at high spl with low distortion
+1 for Hsu Research. I'm very pleased with my ULS-15 Mk 2. I have a similarly sized room with a vaulted ceiling. It has more output than I can use.
REL or Sumiko for music. Easiest to blend and incredibly musical.

SVS and HSU are great for home theater or for 50/50 music/movies. 
I bought 2 rel t7i used with warranty from Best Buy MAGNOLIA. They were like 600 each. I like em. 

     Since your room at 24 x 17 feet is fairly large, I believe 2 good $500 subs will definitely provide much better bass performance than a single $1,000 sub.  2 will not only provide a higher bass volume and impact capacity, it will also provide more accurate and detailed bass that will sound much smoother and natural which will work very well for all music types. 
     By far the best sub system solution I'm aware of, however, is the 4-sub distributed bass array (dba) system.  This is often described as a 'swarm' system that was recommended by bstatmeister and millercarbon earlier.  It's a concept based on scientific research conducted by acoustics experts Dr. Earl Geddes and Dr. Floyd O'Toole and advocated by the Research Acoustician at Harman International, Todd Welti, and the owner of Audio Kinesis, Duke Lejeune.   
     These dba systems are available from Audio Kinesis as complete $2,500 kits (Four 1x1x2 ft subs and a 1,000 watt sub amp/eq) called the Swarm and Debra. But custom dba systems can be created using virtually any 4 subs desired. 
     The main benefits of a 4-sub dba system are that it provides excellent bass response in virtually any room and integrates seamlessly with virtually any pair of main speakers, even fast speakers like planer-magnetic and electrostatic panels.  
     I use the Audio Kinesis Debra 4-sub dba system combined with a pair of large planar-magnetic panel main speakers, which only have accurate and detailed deep bass down to 36 Hz, in my system.  This dba system provides tight, smooth,accurate, detailed, dynamic and powerful bass response in my 23 x 16 ft room that integrates seamlessly with my smooth, accurate and detailed main speakers.  I consider the bass response of the AK dba system as state of the art and sincerely can't think of any aspects needing improvement, the concept really works that well.
     So, my suggestion is to use at least 2, perhaps a pair of SVS SB1000 subs for $950/pr, for very good bass response or use 4, either 4 SVS SB1000 subs for $1,900 or an Audio Kinesis Swarm or Debra complete system for $2,500, for excellent bass response.  Here's an Absolute Sound review of the AK Swarm dba system that contains a very good description of the performance to expect:


I'm not contesting the consensus, but my former listening room was 24 X 17 and my 12 inch B&W sub worked just fine.
Many thanks to all of you for your comments and suggestions. I have decided to explore a single sub woofer for my system. I heard my speakers with a singles woofer a couple of weeks ago and liked the way it enhance the quality of sound that came from them. Although the Monitor Audio Gold 100 have a very nice sound stage, the sub woofer opened it up more. I will audition at the Defiance V and X series and likely purchase one of them. Again, thanks.