I'm with you. The FX1X, FX101, and FX40 were too sibilant for me as well. With the XX series there was a wall of static where the cymbals should be (at least to my ears). Now the FX40 on the other hand calmed down after MASSIVE burn in and I can deal with it now, but it's still more harsh than the CKN70s. These CKN70s are the first headphones that are bright that I've actually liked. At first they were painful to my ears, but now, they sound magical.
I wasn't gonna buy these because I figured since I have the CKN70s there would be no need to. Now you've got me thinking about it. I know you're about to push me over the edge, I can feel it.