Hey Jellofund, your original post is now overwritten? Anyhow, I have listened to both the German Maestro GMP 450 PRO as well as the 8.35D's and I found the GMP 450 much more comfortable to wear, plus it has the larger shells standard from the box, which is a plus. And in my opinion the sound signature of the GMP 450 is even closer to the HD600 than the 8.35D's, plus, the GMP 450's are 300 ohm so they shine with a tube amp, just like the HD600.
And what surprised me, as mentioned, is that they don't even sound awful without an amp. So an option for traveling too.
I would however not replace my HD600 with it, the HD600's are definite keepers..!