Full detailed sound at 30 - 40 - 50 dB

I love the nuance you can hear when listening to music at loud volumes, but unless no one is home, it’s not considerate or feasible to listen at such high volumes. Plus I just had a baby so everyone is always home and volume levels are limited to 40ish dBs. 

Any recommendations for getting the most detail at these volumes? Additional gear or recommended integrated amps?

My NAD 7175PE has a loudness button which boosts the treble and bass a little, and that certainly helps things in the Kitchen. 

My living room amp is a Rega Brio-R which doesn’t have any tone controls. 

Any thoughts? Thanks!