Dleblanc, I can only halfly agree with that statement. Achieving very even frequency response from bass to treble was achieved pretty easily with the HD600 15 years ago. Of course it's not the technical juggernaut the HD800 is, and at the lowest bass and highest of treble there's roll-off, and it's not as adept in micro-dynamics, but hey for something that's 15 years old I'd still take it over an HD800 purely based on tuning. HD800 stock for a lot of people might be fine, but too thin for me, that's my personal taste though. I wouldn't own anything less than HE-400/LCD2 level of bass output and extension. Sennheiser made a very distinct tuning decision with the HD800, they took the treble response from 6khz on up and gave it a boost-- think of it as plateau'd treble.
I'm sure all this sounds extremely condescending coming from a guy who loves the HE-400 and EQ's its treble down for desired effect, but at the same time I'm not spending 1500 bucks for something I find to be fundamentally flawed. It's the same reason why I'm not in any hurry to buy an LCD, because I find its mellowness to be fundamentally flawed as well for such an expensive headphone, although at the end of the day I'd take a stock LCD over a stock HD800 because I find its tuning decision to be less problematic than the HD800.
I guess what I'm trying to get it is I admire Sennheiser and their very technically competent headphones, but I ultimately despise them as a company because in the last 15 years their headphones seem to be getting worse and worse in terms of frequency balance. It's so disappointing they nailed an even sound so long ago, and have since then created headphones that are getting more and more colored. Think what Sennheiser could have done with a headphone as well engineered as an HD800, but without their heads stuck in their asses and falling into the 'more treble = detail' audiophool camp.
The only caveat to this argument is that I have not tried an Anax modded HD800, although I would like to at one point.