You may been "bit stripping" with the Benchmark digital domain VC if it wasn’t used at or above 75% of full output. It should have sounded better direct than the Axiom if it was used like this.
Many hi-end tube and more s/s integrated amps have passive preamps, just volume pot and input selector switch, then it’s straight to the poweramp input section.
As sources today have 2v or more output, which can clip most poweramps, which most just need 1 -2v for full input sensitivity, so there’s no need for active preamp stages.
A Quote from the master Nelson Pass
We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.