"Lower volume not so much"
How low? Do you think you may be in the low volume region whereby some Bass Boost is needed (by all of us)?
Fletcher-Munson analysis, and solutions exist
https://en.wikipedia.org/wiki/Equal-loudness_contour
In the old days, all receivers and all preamps had a ’loudness’ filter, which was actually a ’low volume compensation filter’, based on Fletcher Munson curves, boosting bass progressively as volume lowered (also boosted highs, but bass is more important).
One way to add Fletcher Munson curve to a system without it is this Chase Remote Line Controller RLC-1
it starts at a default volume with no F-M compensation. As you lower the volume below default, it automatically and progressively implements F-M bass boost, in relation to the reduced volume.
Essentially ALL Preamps/Amps need this (modern equipment lacks ’loudness’ filters), and all speakers need to receive boosted bass signals at low volume.
Therefore, different speakers will not solve the problem, different integrated amp will not solve the problem.
Add a gizmo? No one, none of my friends, including myself are able to detect whether the Chase unit is in or out of my system.