"Holographic" presentation

TWo mono amps, or a stereo amp that consists of two highly isolated mono amps in a single box even, may well have better channel separation and less crosstalk, which could work in favor of a more "holographic" presentation, but whether or not this would be heard in comparison to something else or not would still depend.

Assuming quality gear designed well in all cases, using two mono amps is probably a good insurance policy that overall performance of each is fairly independently optimized which should always work in ones favor.

In a nutshell, more can be done better with a single self contained monoblock, with dedicated power supply, etc., than can be done for similar cost otherwise.

I think that speaker placement and room treatment are more important factors determining three dimensionality than whether the amp is of stereo or mono design.

I was comparing two different speakers - and there was a noticeable improvement in soundstage depth and width in one vs the other.

A speaker designer I know says there's a simple explanation for that - our perception of soundstage is determined by the slight differences we hear from the left and right speakers.

The speaker with a flat soundstage had a less rigid cabinet. As such, there is some vibration from the cabinet that is smearing the soundstage. The vibrations created tend to be "mono" like from both speakers and that masks the small differences that were in the original material.

As Mapman has stated, the use of mono blocks could reduce the amount of crosstalk (or mono information common to both channels) and I can see how a similar reasoning could explain why the soundstage could be improved with a mono block design.

Here's a question- what good are dual mono amps when you are using a stereo preamp?

My experience has been that as long as there is very good stereo separation, and the media contains the spatial cues necessary, you can get the holographic illusion. And it is an illusion because holographic suggests three dimensions, while our stereos are by definition 2 channel sources.

Mono amps may not make a night-and-day difference.
Much of the voodoo that we-do (vibration control, room treatment, power conditioning) doesn't fix everything.
Taken together, however, results in substantial improvement.