I bought the Philips Fidelio M1 because of his quite flat frequency response graph :
[Blocked Image: http://img1.lesnumeriques.com/test/69/6923/Fidelio-M1-frequency-response.jpg]
It works very well with the kemper, but I find it a bit uncomfortable.
AKG: They don't have detachable cables, and I don't find this very convenient when playing guitar
Beyer DT770 : has a known problem: the low ends sometimes crackle in the right earpiece. I didn't believe it, bought one, got the problem and sent it back...