I have owned my HD600 for 12-15 years now. I had to change headband and earpad de to weare after 10 years. I believe the Sennheiser HD600 is my best purchase EVER no matter what! I am extremely happy with them. They are great sounding. I truly feel they are shining with my Darkvoice 336SE amp. Great bass, openness, dynamic, instrument separation etc. They are not particular picky regarding amp og source. I love their sound. 
 
I also own Denon D500 lawton mod and Hifiman HE500. Both om which I regard inferior to the Sennheiser HD600.
 
Cant recommend them strong enough!