Can you lower gain requirements on tube amp?

I have a Cary Rocket 88R tube amp (30w tri/60w UL) that requires more gain then I'm used to to get to 'realistic' (ie louder) listening levels (90db+). I have a Promitheus Ref4 TVC passive that I love, but volume knobs at full throttle sometimes still isn't loud enough. I literally need it go to 11.

Specs on the TVC state -48db to 0. I'm curious if I can do something to the amp, ie roll different driver tubes or??.... to decrease the gain requirements? I've also contacted Nicholas at Promitheus to see if he can modify the gain, haven't heard back yet.

I will also state that my speakers are Usher 6381 rated at 87db/8 ohm. The Cary drives them well, but wondering if the speakers sensitivity relates to loudness (ie more sensitive speakers would generate more loudness at the same volume settings?)

I don't want to introduce a tubed buffer into the mix -- tried it and didn't like the sound. Want to work with what I have if possible. Thanks

FYI tubes in the Cary are:
kt-88 output
12BZ7 / 12AX7 / 12AY7 drivers (currently using 12BZ7)
EL-84 / 6BQ5 current source