Subwoofer for 2 channel high resolution system

Bob is right. You need to test drive some of the subs you listed. I tried Velodyne and B&W before a ended up with a Rel. The Rel just blended with my room/system better(even though I run B&W speakers). Good luck!

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?

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.

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.

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 would go with either a REL or the Wilson Benesch.

You will pay as much as a top flight preamp for these, but the Wilson Benesch infrasonic generators are the fastest, most true sounding bass units out there!

they feature they're own amps and have a slew of function capabilities

they can blend seamlessly with box, planar, electrosatic etc...