I agree with you completely. The latest Dolby DD p mixer is incredibly good. From two channel recordings it manages to reproduce the original acoustic with a realistic perspective from 2 channel audio.
Probably the best demonstration of how good it is, is this two channel recording by Tom Scott of his brother Jonathan playing Bach's Wachet Auf from St. Mary's Petworth. The flute division is on your immediate right and the reed plays from the division ahead. The right division is precisely located on your right and the reed right ahead, as it would if you where in the nave of the church. This could not be better even if it where are discrete five channel recording. I find this incredible.
I know you use center spread. However on this rig center spread ruins the effect. I get really good left right and center localization leaving it off. Not only that, this upmixer increases the sound stage depth of the recording, and on many good recordings the sound stage sounds wider then the speaker spacing. I never ceased to be amazed how good it is.
One other thing I have noticed is that this latest versions works on vinyl playback from my turntables. The previous one did not, and was prone to a curious pumping. I have not heard it with this current version.
Now I suspect results may vary, in that in my rig every speaker is very capable. They all sound really similar right across the acoustic spectrum except the last two octaves. Although five of them reach well into the last octave, and the mains all the way to 20 Hz. Although the center is deliberately conceived to be different to the mains, to give it a cone type dispersion covering the listening area. However when you walk across the front stage all three speakers sound identical and I don't think anyone would suspect they use different drivers.
I don't know, but I suspect you would not get similar results unless all speakers have a really smooth response from 80 Hz upwards. In addition all these speakers have an excellent sharp impulse response. I consider that important and often overlooked, and may be significant in causing this technology to work properly.