Title says it all. Is it possible to upgrade from the HD600s?

Here's something that most people don't consider when auditioning/reviewing headphones. Where you place the headphones on your head affects the sound quality. And even more than that, the distance of the drivers to your ears (dictated by the amount of use the cushions receive,) has a huge impact...

Playing around with the frequency response charts at headroom.com makes me think that the Sennheiser HD600 may be the most accurate headphones ever. Anyone agree? It's close against the AKG K701s.  ...

I'm just wondering how much demand there is for one since I'm thinking about putting mine up for sale. I bought it new for $1333 after the review came out in Stereophile in the '90s. (http://www.stereophile.com/headphones/261/index.html) Also, I'm working on making 15 posts in order to be able...