Please recommend a musical sub for me

Hello folks, I am wondering if you could recommend a sub for a music only system. I alternate between four vintage 80s speakers (Spendor SP1s, Spica TC50s, Linn Kans, EPI 100s) and all are classics and excellent within their specific parameters but they are all somewhat deficient in the bass. I alternate speakers depending upon my mood and musical selection. I am running Quad separates (909 power and QC pre) and listen to everything except classical. I would like a sub under $1000 (new or used) that is flexible enough to blend with these speakers for a music only application. I am not interested in reproducing earthquakes and sound effects, just a seamless integration and a fast, quick, precise bass that keeps pace with the music and doesn't seem to be disjointed from the speakers named above. My room is fairly small (13 X 14) so this might be an important factor in your recommendations. Thanks for your advice.