couple of weeks ago I listened to the hd 600 amongst others using a modded xing sheng 703b [highly modded] comparing them firstly to a set of grado 125i's .......and lastly to the grado rs1e.
the hd600 sounded thick and slow almost syrupy to 125i's and frankly against the rs1e were undynamic and muddled , which I though was a great shame as there often highly regarded. ...ended up with the rs1e's.