Of the headphones i've tried in the past:
Slightly Overrated:
grado sr60:it sounded ok to me but expected to be better/more refined after all the comments here)
koss ksc75:good value for money,but i've read in a thread that some people would give much more money for them....No,i don't think i would give more than the 30 euros i spent.
Underrated:
k701/702,k601,hd650:i'm thinking to get a k601 for myself,i liked it's sound quality.K701 is seriously underrated in my opinion(although i've never heard it with a good home setup,only out of a profesional audio equipment)
hd650 is very good headphone,and is not boring if driven properly.
Most overrated & most underrated at the same time:
hd800/hd600
I think the hd800 sibilance is not a real problem but is a problem that was created by some members who had the bad luck to experience sibilance with their setup,and then other hd800 owners were affected and thought that their hd 800 is sibilant(but i'm not sure because skylab seems to be very experienced and he tried it with different set-ups,and there may be differences between different hd 800's).On the other hand,i don't think that it is sooooooo good,the best headphone ever etc(although i don't have experience with other very expensive cans)
But i can't understand why almost nobody complained for sibilance with the hd600.My hd 600 were sibilant out of many setups i've tried them in the past.
The hd 600 can be sibilant,especially if you drive it out of some integrated amplifiers and consumer av recievers.