Dunc, not this argument again.
Seriously, though, while I know that the Orpheus headphones are electrostatics, in some ways their sonic characteristics sounded to me as though they were an extremely refined HD600. Highs are smooth, midrange very sweet, bass taut but pushed forward a little bit.
Given proper amplification the HD600 can be compared to the Orpheus, though I don't believe it could ever surpass the Orpheus no matter what. I really thought the Blockhead was in the same league as the Orpheus, though perhaps they are at opposite ends. With the Cardas balanced cable perhaps the Blockhead/600 come even closer to rivaling the "Big O."
The problem I would have with the Cary/600 combo is that it gets to the point of emphasizing parts of the 600 that are already disliked by some, and even for enthusiasts, emphasis of these parts could make them dislike the headphone. The Cary is a sweet-sounding headphone amp, warm, enveloping. But put too much lush warmth with the HD600 and you might just have a problem.
I have yet to hear the R10 in good circumstances, but from what I've heard, the three set-ups at the very top of headphone listening are the Orpheus, Omega2, and Blockhead/600, in that order.