Bo1972 - if it were possible I'd invite you to come listen to my rig, since it is far from flat and quite nicely 3D - perhaps not as good as your amp, but still very good compared to many other that I have listened to.
I attribute this 3D image to the upgrades in cables - power/interconnect and speaker and very much to the Gershman Acoustic speakers
I do have several tracks where the instruments are positioned very accurately in the sound stage with the venue acoustics adding significant height to the performance - just as you described.
The most recent improvement was due to a change in the mains connectors on my furutech 10 gauge cable, which improved the 3D image to levels never experience before.
Granted - the amp out of the box with standard power cords has a flat 2D presentation - but then so do many other brands.
The biggest improvements I have made with my rig is with the power cords - they have transformed the whole sound.
I do believe that your opinion is based on what you have experienced - but then again - so is mine. So I think we will just have to agree to disagree.
The nice thing about Agon - there are many different opinions available for people to evaluate.
Regards.