Shadys wrote: "I have a pair of magnepan mg12s that do a great job at image depth provided I get them out into the room, say 3+ feet from the wall. With good recordings the image depth often appears to go beyond the front wall."
YESSS!!!
That is exactly what I have found with dipole speakers. Once you get beyond about 3 feet (and 5 feet is REALLY good), just about everything - including in particular the soundstage depth - improves. Here is what is happening, I think:
The ear/brain system judges the size of the room by the time delay between the first-arrival sound and the "center of gravity" of the reflections. As you move dipole speakers farther out from the wall behind them, you are delaying the onset of the reflected backwave, and thereby correspondingly pushing that "center of gravity" back in time. The ear/brain system interprets this as "you're in a bigger room", and thus super-imposes less "small room signature" on top of the recording.
Along similar lines, in designing a recording studio, the acoustician tries to prevent significant early reflections from reaching the recording engineer's ears in the control room earlier than the natural reflections in the live room where the recording was made. This way the recording engineer can hear the natural reverberation of the live room without the (typically smaller) control room superimposing a "small room signature" on top of what the engineer is hearing through the monitors.
I take advantage of this characteristic of human hearing in some of my designs by bouncing reflections off the ceiling, thereby adding time delay to those reflections similar to the backwave of a dipole speakers pulled out into the room a good five feet or so. You can hear the soundstage depth collapse when the additional up-firing reflections are turned off.
Duke