The best "imaging" speakers?

The best you are there experience I have had was in the 90s with the 2C3D systems which contained Avalon/Spectral/MIT/ASC products, many of which you already own :-)
I have heard the same setup with Thiel CS6 speakers to similar effect.
I am getting very close with the Thiel CS2.4s, Bel Canto DAC3, Ref1000s and all MIT cables in my reference room.

note: I am a Thiel and MIT dealer, as the original poster knows.

Since sound from the speaker radiates around the edges of the speaker then you inevitably get edge diffraction which interferes with imaging.

There are two ways to deal with this:

1) Small narrow baffle so that the edge diffraction occurs very early in time and does not interfere with our ability to determine the precise source of the sound. A small box like a Bose Acoustimass achieves this and so do triangular and narrow baffle speakers to a lesser degree. Generally most speakers do not image well at certain frequencies due to the interference of the baffle dimensions.

2) Infinite baffle. This requires building the speakers into a wall or technically a "half space solution". In this case there is no longer an edge diffraction problem and the imaging should be unimpeded or as good as theoretically possible. (Of course an infinte wall is impossible so ultimately the imaging may be impeded by the side walls, ceiling and floor - in practice if you can keep about 4 feet away from the walls then imaging will be about as good as it gets)

A few years ago everyone was pumping line source speakers as imaging champs, like the Pipedreams and such. They imaged very good side to side and front to back and had dynamics like a Klipshorn, but the size and scale of the image was way too big (as Jax2 said). Picture a 3 foot wide nose on the singer "standing" in front of you. Not realistic at all, after all. I know there have been strides made to reduce this scale problem by tapering the response of the drivers at top and bottom, but it is still a bit spooky to my ears and not really natural.

Bob

About the best I've ever had was my Gallo Reference 2s. You could be just about anywhere in the room and see/hear the performance from that vantage point. The performers didn't move, your perspective of the performance changed, it blew me away. I'm getting my new Reference 3.1s dialed in, and they are starting to get there, just not yet.

Martykl,

Narrow baffle floorstanders with extreme cabinetry can also mimic this effect.

Perfect description of the Totem Arros, I think.