With a sensitivity of 85dB your current speakers will never sound properly alive at low volume. That's just the nature of low-sensitivity speakers. Been there, tried it (with an array of different amps) and failed utterly.
The only way to achieve engaging sound at low levels is to use speakers with a sensitivity of at least 90dB. 95dB would be better, 100db better still.
The only way to achieve engaging sound at low levels is to use speakers with a sensitivity of at least 90dB. 95dB would be better, 100db better still.