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. 
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.