The first obvious question relates to system set up. Have you eliminated hard surfaces at the first reflection points on the side walls, floors and ceilings? They are a big contributor to sibilance, overall brightness, and 'distortion'.
Second biggest contributor (If not the first - I'm not familar with your speakers), are you listening to your speakers on the speakers axis? Many speakers are hot on axis and must be pointed straight ahead, or something in between. On occasions I have gone so far as to toe my speakers in so that the axis crosses in front of my listening position to avoid both sidewall reflections and still listen well off axis.
Lastly, have you listened to other sources on your present stuff and found the presentation to be with out the same sibilence?
I'll not comment on the wires. While I've found wires can seem to be a contributor to brightness on occasion I have no experience with your equipment. Perhaps someone with your stuff will have first hand knowledge, but FWIW I've never been able to tame sibilence with just wire changes.
Second biggest contributor (If not the first - I'm not familar with your speakers), are you listening to your speakers on the speakers axis? Many speakers are hot on axis and must be pointed straight ahead, or something in between. On occasions I have gone so far as to toe my speakers in so that the axis crosses in front of my listening position to avoid both sidewall reflections and still listen well off axis.
Lastly, have you listened to other sources on your present stuff and found the presentation to be with out the same sibilence?
I'll not comment on the wires. While I've found wires can seem to be a contributor to brightness on occasion I have no experience with your equipment. Perhaps someone with your stuff will have first hand knowledge, but FWIW I've never been able to tame sibilence with just wire changes.