sibilence in right channel on occasion

Its most probably the record. You could switch the L vs. R leads and check it out that way if you suspect the cartridge.

Interconnect and power cabes are the most common cause of this. What cables are you using?
Bob

I would also check that your speaker drivers are torqued correctly. Snugging up the screws on several of my speaker's drive units has alleviated small issues.

I had this issue with some vinyl as well. I adjusted the azimuth and added a better isolation system to my TT. This solved the sibilance and slight white noise in one channel.