Neither the SRH940 nor the Amperior have sibilance issues, although they are both pretty bright. The Amperior is more in your face due to the smaller soundstage and seems a little less detailed, once again on account of the soundstage. The Amperior has more bass and is therefore technically warmer than the SRH940, although I would still not call it a warm headphone (compared to other truly warm headphones like the HD650). I'd say that the Amperior has a more neutral sound than the SRH940, which is brighter.
I highly disagree with this statement. I own the SRH940 and I find it to be not sibilant what-so-ever. I have tried the Amperior at a local Head-Fi meet and I couldn't stand it. Female vocals were so sibilant that they were unbearable for me. Listening to Joanna Wang's "Lost in Paradise" sounded terrible because of this sibilance issue. I also know that I'm not the only one who finds the Amperior sibilant.
Edited by miceblue - 12/17/12 at 5:35pm