of course EQ isn't just a magic fairy that turns things into others. else I wouldn't ponder about getting the hd800 at all ^_^. I would go and EQ a porta pro.
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
h34r:
but in this case, I would mostly reduce the high-mids and trebles of the hd800(what everybody has been doing with warm rolled off amps), something an EQ does very well without creating much "negatives". well a little phase shift with an analog EQ but the same as a colored amp would do, exactly the same. and the same or without phase shift, and with less distortions on a good digital EQ.
I guess I'll have to try and steal a pair from a willing victim so that I can try. guessing will only leave me with doubt. (not that I'm crying because I'm "forced" to use the hd650 ^_^)