One of the more elusive hallmarks of a great system is its ability to let instruments and voices breathe.
When we hear a great recording on a stellar system we often refer to this breathing as air around the sources of sound.
The question, then, is how to increase the amount of air around each instrument. In its simplest form we can say with some confidence that loudspeaker setup plays a major role. Get the two speakers too close together and the tiny soundstage it produces hasn't enough room to accommodate more air.
Working our way down the list of importance, in a digital system I've noticed DACs play the most important role, followed in a close second by the cables connecting the system together. In a vinyl based system, I would put forth the idea of the phono stage having the greatest impact on air, followed by the preamp.
One of the most obscure sources of air turns out to be the power amplifier. At the end of the proverbial day both digital and vinyl benefit from the design of the power amplifier. Here I don't look for increases and decreases in air volume. Rather, with power amplifiers I listen for masking. Power amps can mask or cover up the volume of perceived air.
There's more, but these are the major factors I've noticed over the years.