Theoretically, How to Reduce Gain without Minimal Impact to Sound?

I am finding that the granularity of my volume control in my chain is not fine enough as it is currently configured. I have my source set to maxed volume and Gain to High, and I have the volume attenuators on my monoblocs maxed out. The preamp is what I use to adjust volume, and when I use the tube buffer mode (Schiit Freya+), I am finding that it is hard to get a precise volume level I want sometimes.

What would you recommend as the best method to get better volume control granularity without affecting sound quality? Should I cap the volume level at my (digital) source to something less than max/100, like, say, 65, while leaving Gain to High? Or should I leave the digital volume maxed, but change Gain setting down to Medium or Low?

Or dare I leave the digital source maxed out, and turn the volume dials down on my monoblocks to 3/4 or 1/2 (going to guess this one is a no-no because volume attenuator pots are, "throwing sound away")?

Using passive or solid state buffer modes on my Freya+ are not an option. I lose a ton of imaging benefits when switching away from the tube buffer mode (which, yes, I know, is a lot louder than the passive or unity gain solid state buffer modes).

-Ed