I have a M565C and I like it very much. Also have the M1570 (open version) and the latter is overall my favourite headphone (I even preferred it to Arya Stealth, but I have not owned or listened to other hi-end headhones of any brand, nothing over 600€ apart from Arya). M1570 and M565C have an 'house' (warm) timbre and they are not so far apart, despite the consistent difference in price. Yes, the M1570 is the better headphone, anyway.
In my opinion the M565C has very few defects in FR, the graph above is good and reflects (more or less) what I'm hearing: It has a little bump that I have spotted at about 125 Hz (and shelved down of 0.5 db), and it also would benefit from a touch more bass (50Hz and below); I' ve sligthly lowered the 3.5Khz area (with a pretty large bell), according to my personal preferences. Highs are spot on, the right amount and for me no need to eq them. All of that by ear, because this is the first time that I see a FR graph of the 565C (thank you someguy). Overall, one of the headphones that I own (or have owned in the past) that require the less amount of eq to sound good. Very good dynamics as well. I've preferred the M565C to HD600 and HD650, apart from comfort (the headphone is light an do not clamp much, but the earcups are too little for me).
Personal opinions, of course.