Ozzy, the same here (hear). I recently bought a NAD C 326BEE intergrated amp.; burned it in for 4 days nonstop. Played some Diana Krall and noticed that most of the sibilance I always heard was almost gone. I attached a 6v battery with 10k cap to the amp and that eliminated the remaining sibilance. All gone, banished. There is much more to be said about this tweak but I'll end with, I'm really happy I found out about this tweak.