Anything that resolved low-level detail. Crossover-less speakers help in this regard and poor crossovers and poor passive parts (XO, terminals, wiring, etc) kill this. The result is having to listen at "louder than live" volume to compensate. Great speakers sound great at all volumes. No loudness button is needed.
Actually 60-70 dB SPL isn't that low, especially for acoustic music (jazz, classical, folk). I'd say 50-60dB is pretty low (night time volume). I think you'd be surprised that a lot of us aren't listening at 85-90dB SPL or louder. I don't even listen to death metal that loud (82-ish). I don't need to.