That statement is absolutely personal and in my opinion completely incorrect. I find the 600s to be boring, I rather the 650s, 800S or even the regular 800. What you should've said is your preferred pair of Sennheiser headphones are the HD600, no doubt.
I have the 600's paired with a Schiit Bitfrost multibit and a Bottlehead crack tube amp. I have never felt a desire to get another pair of cans (when purchased, originally demo'd HD600's, HD650's and DT880's).