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
Look at REL, seemless integration and it will be perfect for your monitor audio gold 100 and your listening preferences. 

https://rel.net/shop/powered-subwoofers/serie-ti/t7i/
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).
https://www.paradigm.com/en/ported/defiance-x12