Can't remember who it was @Claritas and somebody else
I gave in and bought the HD600, it's tonally very well balanced thanks!
Glad you enjoy it.
Re: HD600 vs HD650 cont'd. HD650 does have a slightly more filled in soundstage, which might matter if you listen primarily to large-scale orchestral music. (I suspect that the soundstage difference is a by-product of the different bass response.) HD600 is a little more neutral in the upper mids, which matters a good deal to me because I listen to solo piano more.