Actually, it is not best to have your speakers well out into the room as long as the first reflection points on the front wall are damped. The position of the listening chair is way more important. What happens is bass being omnidirectional changes it's nodal pattern as you change the distance to the front wall. Usually you will notice a change in the quality of the midbass. Paul Klipsch always recommended that you put his speakers right up against the wall or in a corner, Cornwall. I think most of the tower speakers I have heard do well 2 to 3 feet away from the front wall again as long as the wall is treated correctly. My own speakers are planar dipoles. Since they are towed in the distance to the front wall is from 2 to 3 feet. The wall behind the speakers is covered with acoustic tile. I also have total EQ control over the systems frequency response and I measure the system's performance.
Vision and hearing have a very complex relationship. What you see will affect what you hear. Close your eyes when you listen and imaging will become for distinct.
The soundstage should always be as wide as the speakers unless some slick phasing is done as in Roger Water's Amused to Death album. If it is wider you are listening to reflections off the side wall which is bad because it ruins image specificity, distinctness. What most people interpret as depth is really echo added to the recording or venue the recording was recorded in. Echo makes you think you are in a larger room. Most systems do 2 dimensions fairly well. The third dimension is not the echo. It is the sense that the individual or instrument is a three dimensional object standing in space very much like a visual hologram. This is an effect that very few systems can manage. It also requires a good live recording. Studio recordings are usually all over the place.