Anyone listen to Zu Audio's Definition Mk3?

Germanboxers, what you are asking for is the holy grail of audio IMO. Room and power are important elements beyond simply amp and speaker interactions. What people lost in the dust flying around Glory's contrarian testimony is that his own personal achievement of this very goal was realized largely through power and not simply amps, cables, sources, etc. You two should chat.

Power and room acoustics are really really important.
After years of listening direct from the mains in an area with a highly corrupted electrical supply I installed a c.$6000 power conditioner which opened up the soundstage and lowered the noise floor, but as with all conditioners, there was some pinching of dynamics due to restrictions in current supplied to power amp during peak passages. I recently progressed onto installing a standard $600 (small fraction of cost of conditioner) balanced power transformer; soundstage expanded a little further, but now unlimited dynamics.
This change has NOT been subtle, so my advice is go for a cheap 4kV (at least) transformer to give your system totally balanced power and you will not be disappointed.
On the subject of room acoustics, I really object to dedicated listening rooms. Great if you have the real estate, but most of us have to live and listen in the same space, and you want to welcome, not banish the family.
So for me the SpatialComputer Black Hole anti-wave generator has been a Godsend.
With my current Zu Def2's they'd always sounded great except for bass node/standing wave issues esp. around the 27Hz region. Rather than redesign the room or load it with obtrusive traps etc., I gave the Black Hole a whirl.
It has really tamed these bass excesses so the whole musical spectrum shines. On acquiring the Def4's I am even considering one or two more units to totally subjugate this acoustic issue for good.
Happy to expand further on these issues, but total cost of c.$2000 has transformed my system, taking it to a level that spending 10x this amount wouldn't have acheived.

Spirit - did you eliminate the power conditioner in favor of the balanced power transformer, or are both employed? Also, do you plug all of your equipment into the balanced power transformer, or just some pieces?

Rockadanny, I've eliminated the conditioner completely, although one possible variation might be to plug the power amp into the balanced transformer, and the sources/pre into the conditioner.
From what I gather, most people run one or the other.
Main caveat with the transformer is that the copper windings (my industrial unit is 60 lb) take time to bed in, so treble was hard for about a month, sweetened after that time, now I would never go back.
I am also looking at a pro based unit that supplies 8kV (possible overkill here) weighs 180lb! and is in the same price territory as my previous conditioner.
My $600 unit is the biggest bang per buck upgrade in my system, and that's in the context of a $60000 system.

Agear, I'm fully aware that I'm seeking the "Holy Grail"...aren't we all? I've been on the merry-go-round for 25 years, chasing one more elusive "attribute", usually at the expense of another. With the Zu's, however, I don't feel any desire to risk all the wonderful, music-serving attributes for the "possibility" of acquiring that last one. If this comes across as unnecessarily cautious, it's because my audio journey has highlighted how easy it is to find myself back on that "merry-go-round".

I would love to hear Glory's experience regarding that final attribute. Why has Audiogon eliminated the ability to e-mail a fellow member?

I do remain skeptical that my path lies through solid state amplication for a variety of reasons, but I'm cautiously open-minded to it. Keeping the hyperbole to a minimum, more often than not (though not always), tube amplication has brought me closer to my music-serving attributes, whereas quality solid state more often required the sacrifice of at least one music-serving attribute to gain another.

A recent example: I purchased a pair of Clayton M200's (pure class A, 200w/ch) to use as a "change up". It's certainly overkill from a power standpoint with the Definitions, but by most accounts the Clayton amps are truly outstanding SS amps. There is no grain that I'm overtly aware of, harmonics are very good, bass control and impact is impressive, highs are open and extended. Yet as good as the Claytons are and given the clearly superior and visceral bass, I "feel" that I'm giving something up in comparison to the Atma's. It could be (and probably is) simply that the Atma's are a better match for THIS speaker, but I've had many more experiences similar to this over the years.

Agree that room and setup are critical and have had mixed results via better PC's and cables. I currently use PS Audio Premier for all but amps, though sometimes plug the M60's into it as well with no noticeable deleterious effects.