Well, I've got a different take on what 'holographic' imaging is, as opposed to 'soundstage'.
Soundstage, for me anyway, is represented by highth, width, plane of front of the image, and a feeling of some depth behind the plane of the speakers. The size of the soundstage can be maximized to where it appears outside of the speakers and up into the corners of the room. This can be caused by out of phase information inherent in the recording, the sound reflecting off room surfaces, and the type of speakers (bipole, dipole, omni's, etc all of which have different radiation patterns). But none of this is necessarily representative of 'holographic' imaging.
My definition of 'holographic' imaging means the reproduction of a sound (it has to have its origin in the source) which is not only located appropriately in space, it is well defined, and takes on the appearance of a full dimensional tone. The visual parallel would be a cardboard image of a person 50 ft away and a live person 50 feet away. You can tell the difference, unless you have a heavy morning fog, or rain, etc, to obscure the difference.
I think any well put together and set up 2 channel system can do excellent soundstaging which will have good front to back spacing, BUT to make it really 'holographic' you need a system which is highly resolving.
Its the tiny detail lost in most system's that rely on room reinforcement that make a difference. Some speaker types can never get you to 'holographic' (omni's would be a gross example of great soundstagers which are incapable of truly 'holographic' imaging) and some speakers (such as direct cone or horn speakers) which are blessed with high resolution can easily represent the full image. It is the reproduction of the very subtle signal that takes you all the way to holographic imaging.
I think its far less an issue of electronics, given a reasonble level of quality, albeit tubes or ss, than it is in the transparency/resolution qualities of the speaker.
But, FWIW, to my ears, you can't beat highly resolving speakers with cone drivers and tubes if 3D imaging is your goal. There is a lot of things they might not do for you, but holographic imaging won't be one of them.