Thank you Acix for all your information regarding the gmp 8.35D.
After reading your review and a couple other reviews (there aren't many) I decided to buy the GMP 8.35D, to replace my sennheiser HD25-1 II.
I found the HD25-1 not really suited as a headphone outside DJ applications and such, it goes loud, the bass is tight has pretty good detail but the sound is pretty hars (sibilance! and way too forward mids) and there is no soundstage whatsoever.
The HD25-1 II only works for really laid back, and warm music IMO, for instance hars metal and rock will sound way too forward and hars. Not sure what all the praise is about.
I'm pretty sure the GMP 8.35D will sound much better, but I'm still a bit concerned about sibilance, is the sibilance less than the HD25-1 II?
Compared to the DT770 pro 80 ohm the HD25-1 II is still on the smooth side, but that little bit of sibilance is still a deal breaker for me.
Anyway I will hear for myself in the next couple of days!
I don't remember much sibilance out of the HD25 II. In my experience sibilance can be a cause of the recorded music, or just lower bit rate. Anyway I'll recommend you to try the 8.35 before you buy.