Thanks ,I will start to toy around with some of those ways & means of elimating the ground.There are enough things to do that something should show up along the way,if there is a grounding issues that is.
Regarding sibilance ...
I have GS 10s, Arcam FMJ CD/Pre/Monoblocs.
When I tried Nordost Red Dawn ( rev II ) speaker cables,
the sibilance was painful. Bottom of the line Kimber speaker
cables, or better, 14/2 romex ( solid copper electrical wire ),
and the tweeters are smooth as silk, very articulate.
I went back and forth 20 times -- how could $800 speaker
cables sound significantly worse than romex, at 12 cents a foot?!
Well, they did.