Subwoofer for 2 channel high resolution system


What sub is suitable for music. Would like something that would mate well with a system that is transparent portraying excellent sound staging and imaging.
Basically I am looking for a first rate sub for music. One that will disappear, but add the bottom that will take my system up a notch.
Also need balanced i/o, and a high pass to amplifier.
pedrillo
The REL Studio would be a sure bet. Amazing how it transforms the whole soundscape! I also tried the Stentor and Stadium, but could not come close to the Studio.
I am enjoying a Rel B3 with my modest 2 channel system.

The B3 is purely a very low octave "augmentation" in my system.

Sorry, I do not know about high pass or balanced inputs. The Rel works so well in its recommended manner that I have no desire to try it any other way.

Room placement made considerable and easily audible differences, in both quantity and most importantly quality.
I would go for either a Rel Studio or Stentor. A Stadium(no longer made) may work also, depending on you're system and room size.
Which sub's are of higher caliber? Wilson Benesch, JL fathom, REL, Velodyne, Revel, Kharma, Martin Logan, Paradigm, Sonus Faber, NHT, Wilson Audio, JBL, HSU, B&W, JM Labs, Tyler Acoustics, Von Schweikert, Avantgarde.
Which ones are the fastest and natural sounding?
From what the mags have been saying the JL Fathom's seem to be the ones- do audiogoners agree? If so what else is in that league?