Too Much Gain the Issue ? (preamp and amp)

I have a Cary SLP-05 preamp- 24db gain with balanced and 17db single ended.  

Using a Pass Labs XA30.8 (26db gain) and even with the 17db of the single ended output of the Cary preamp the sound can frequently be sibilant in the upper midrange.   

Have not had the sibilant sound with other amps (Parasound JC5) but did lower the gain on that amp to 50% of dial.  

Thanks.