Many thanks Cal, for letting me try them all today. ;D All were driven by an SPL Phonitor with Cambridge Audio Azur 740c as the source.
First one I tried: the
Ultrasone Edition 8.
It was a bit fiddly, I had to remove my glasses as the cups were small. I also didn't get a very good seal on the right cup, so I could only get enough bass when I turned to face right.

Very fast, bass was not as powerful as the Edition 9, which is better for me. Not exactly my cup of tea though, especially since it doesn't like my head shape. But I did prefer it over the Edition 9.
Next up,
Sennheiser HD800.
Woah, comfy! Probably the most comfortable I've tried yet. It really envelopes your ears with no excess pressure anywhere. Detractors call the HD800 bland, soulless, unengaging; I call it the reverse. Maybe it's the Phonitor, maybe it's all the insane tweaks applied by Cal, maybe it's the sound signature I was looking for all along, but I instantly connected with this beautiful German. Taut and accurate bass, sweet engaging mids, extended treble and expansive soundstage, my AD2000 was left weeping in one corner except for one detail (I'll cover that later). No specific area calls attention to itself, it somehow combines neutrality with a natural sense of musicality. It sounds REAL.
After that, the
Grado PS-1000 steps right up.
Rock on! Bass hits hard and hits fast without tainting the midrange. Don't headbang too hard though, it is a heavy beast and might slip off your head. The bass combined with the natural midrange and sparkly treble make it the best among the wallet-busting trinity for rock, metal, anything high in energy really. Not as natural as the HD800, but it makes you want to groove along to the beat.Those looking for emotion, musicality and enjoyment over neutrality must try this hunk of a headphone.
Next was to try the Phonitor with some other cans...
Like the rare
Grado RS-1 Vintage S.
Now I know why people turn to the RS-1 for rock. Super upfront and lush mids and solid bass make for an irresistable headbobbing experience. Someone mentioned that the AD2000 was as if the singer was right in front of you, for the RS-1 Vintage S it was like she's on your lap whispering sweet things in your ear. I just couldn't believe how much more forward a headphone could be in the midrange. Definitely a keeper.
What about my
Audio Technica AD2000?
Left crying in one corner after trying out the Crème de Crème. However, the Phonitor brought out the best in the midrange, sweeter and more forward than my Stello HP100. I still prefer it for female vocals, even over an RS-1 or HD800. The neutral Phonitor may not be the best match for the AD2000 considering the Audio Technica's light bass.
But what about the 30 year old
AKG K240 Sextett?
Monitoring amp + vintage monitoring headphone strut their stuff with aplomb. Tight, impactful bass combined with lush mids and natural treble make it a very musical jack-of-all-trades if you don't mind the small soundstage. Like the RS-1 Vintage S, someones Old is Gold. The Phonitor did not stumble when confronted with this 600 ohm granddaddy, but in the words of someone else who tried the pairing with the volume knob at 10 o'clock: "wow, so soft!"

He had to cranked it up to 1 o'clock.
Once again, many thanks Cal. I told myself my next major upgrade would be in two years time, but this visit may just hasten the upgrade process...