sibilence....any cures out there?

From my experience, Nmmusicman's advice applys to all speakers and all systems. I would add noise caps and RF blockers. I would specify at least two power conditioners on different circuits. I would and do place big bricks on my power conditioners since vibration is also a factor. Low humidity is another factor which is diminished by Spring (static electricity). Get rid of RF and AC noise, vibration, and static electricity and what do you have left? Music if you are lucky.

Its time to upgrade.

Don't believe it. Tweeking is fun and worthwhile.

I ended up curing my system's with less toe-in and also interconnects. For me, interconnects were very frustrating and costly to evaluate and I feel extremely lucky I ended up with ones which mate perfectly with my system. Now I can listen to Diana Krall and Eva Cassidy "Live at Blues Alley" without being bothered by sibilance. YMMV.

Yep. Toe in is cheap and easy and doesn't involve any sort of Voodoo.