Well, sound. But what I have been looking for has changed radically over the last 50 years. At first it was slam, then ethereal treble, details and slam and now musicality with details in the correct perspective, midrange bloom and detailed natural bass.
In the most recent 20 years I went out listening to real acoustic music to align my senses to real music. It had the greatest effect on my values and ultimately provided the best guidance for me to choose the very best (that improved all genera of musics sound) equipment. This is what lead me to Sonus Faber for speakers… then helped me choose supporting electronics.