That diagram (in it's own crude way) is describing clipping.
And I already posted power and distortion figures for the Magni. It's not going to clip with the HD700.
I'm guessing what you're really trying to say (in your own peculiar way) is that for you, the HD700's treble can be a little hot / peaky - so you'd correct it with a "warm" amp with rolled off treble. What I'm saying is that you could do the exact same thing with the Magni (which you describe as the worst set-up), simply by giving it an EQ cut to compensate. Cheap. Tuneable. Clean power.