I agree with tecknik and some others in regard to everything ultimately contributing. One thing that isn't mentioned enough is controlling equipment resonance. This ime cleans the stage up considerably. I've tried a lot of different things & currently use isoacoustics feet under all of my equipment. Each piece of equipment sits on it's own corian platform & each platform rests on ceramic balls. Although that probably seems excessive, the results are in the amp/preamp upgrade neighborhood.
The most important factor in soundstage imaging
Everybody wants a system that images well. There are many discussions here positing equipment changes that will improve imaging. Some people think the magic wand is cables, others are sure it’s the preamp, and the ones that don’t think it’s preamps, think it’s amplifiers. And, of course, speakers are (correctly) mentioned.
However, the single most important factor in audio stereo imaging, is increasing direct radiation and decreasing reflected radiation, by moving the speakers away from the back wall, and away from the side walls.
However, the single most important factor in audio stereo imaging, is increasing direct radiation and decreasing reflected radiation, by moving the speakers away from the back wall, and away from the side walls.