It seems that no matter how hard we try to emulate something or try to create the sound entirely before the power amp, the power amp itself will always be a contributor to the sound. It seems that whatever the speaker wires are connected to, whatever is actually generating the power and directly pumps that power thru the wires and moves the speakers is vital and central. You can't model that stuff. It's yet another critical stage where the "rubber meets the road".
And a word of advice to anyone with a new power amp... NO electronic device sounds correct when it's brand new. Many electronic audio components need time to break in. And even a well broken in device doesn't sound its best when you first fire it up cold. Sometimes it takes 20 minutes for everything to warm up and stabilize. You just can't power up an amp and judge it, even a Mac. It'll sound good, but it'll sound better a few minutes later. Brand new stuff can sound relatively stiff, harsh, and bright and lacking in warmth and "bloom" and dimension.
I think that new electronics like 50 to 100 hours of run-time for the capacitors and other parts to settle in. If audio is being pumped thru the gear, the break-in period is that much more effective. Tube devices sound best after 10 to 20 minutes of being on and running.
And I won't even get into the metaphysics of having lots of good music played thru electronic devices and having a positive effect on the sound quality.
And I have to agree, there's something to the Mac's output autoformers (an autoformer is half of a transformer). There's no way that they DON'T contribute to the sound of those amps.
... and it's just like any other day that's ever been...