Great Musical sound, outstanding comfort and build.
The HD600, HD650 and Q701 are in the same class of higher end sound. The rest of my headphones fall below. The next class is HD595 and ATM-500. I will say my QC15 are fantastic noise cancelling but with major quality issues of one side quiting out.
Out of all the headphones I have, I find the HD600 the most enjoyable; The HD650 are at times better but overall I enjoy the HD600 the most, I have SR-60, SR-80, HD555, HD595, HD600, HD650, AKG Q701, ATM-50, Bose QC15 and some various earbuds
There is always better; but these are great headphones