I will say E3RMIT, that with the EAR Yoshino and the HD650s...even with a laptop and the HD650s...and the exact same music thru the 800S, I immediately get a sharp high pitched searing in both ears. Those 800S and that 4.5db in the 5-6khz range or something in that range is definitely causing me issues. And I have heard a new pair of HD820s and 800S elsewhere as well.
I think that is just me...from the various forums and discussions I have had with owners/former owners of the 800S I think a number of people have struggled with the treble...but still really liked the headphones. Frankly, I still like the headphones a lot. They're awesome...but for this one element. Even some extra bass would be more of a 'nice to have' but not absolutely necessary for me.
However, the 800S just hurts (I got tinnitus from listening to them at volumes low enough to hear my wife typing 5 feet away)...I have never had tinnitus before these headhones, and after I noticed it got worse after 60 minutes of low-listening, i have since stopped using them other than to test for this reduction. The ENT doctor has said to wait 6 weeks to make sure it goes away first.
I am going to figure out this treble thing...and with a couple more attempts, if they dont work, I will sell them.