Too Much Gain the Issue ? (preamp and amp)

24dB is an awful lot of gain for a preamp. 26dB is sort of a surprisingly high gain for a 30 Watt SS power amp. Yeah, that might not be the most optimal match - but the volume attenuator on the preamp should keep the amp's input stage from getting overloaded and causing the sort of sonic issues you describe. So as @erik_squires mentioned, your main artifact of too much gain should just be noise floor. 

The Cary is tubed - LOTS of 6SN7 - so you can tube roll to try and mitigate some of that sibilance. If you have Electro Harmonix 6SN7 in there now, then starting to replace them with any decent vintage tube should help a lot. 

In modern era, preamps with gains over 20dB (almost always tube based 6SN7s or 12AX7s) are sort of an awkward fit. 

You have a tube preamp and I am the only one advising you to roll those tubes 😂

I believe these preamps ship (at least they used to) with Electro Harmonix tubes which are great to liven up a dull/dark system but could very well be a bad match in yours. Adding attenuators can lower the noise floor but won't help the main issue you cite. 

Preamp tubes are optimized- all spots have early 50’s Sylvania 6SN7 GTA. Smooth as glass.

Tried putting the EH, Ken-Rad and Raytheon in and no help.

OK, that's fair and sorry I doubted you! I have 1950s Sylvania 6SN7GTA in my collection, and can confirm they're smooth. I was hoping you were using EH because that would have given you an easy move in the right direction.

I roll several components in my main rig, and some combinations just don't work great for whatever reasons. Sometimes you can mitigate a bit with tube-rolling, but it's most important to find components that mesh well together. And it's not always JUST the amp & preamp pairing either - upstream (phono / SUT / cartridge) and of course downstream (speakers) are also big players in whether the whole system gels together. 

The Cary is already producing the gain; attenuators can help push noise floor hiss (NOT hissy treble) down and enable more volume control range but OP didn't complain about those issues, and they likely won't do anything to address the reported sibilance. Getting a super-low output MC to force a "need" for the high gain is also unlikely to resolve the issue here.

As OP reports clean smooth sound with XA25, he probably already has his answer - the Cary & X30.8 might just be a bad match.