I agree with all; not just to agree, but it all makes sense. So much depends on the room size, type of equipment, room treatments; maybe even type of music.
About a year ago I bought 30min from Jim Smith (Get Better Sound). Nicest man ever; he wouldn't end the conversation until he thought I truly understood his suggestions. His #1 was remove the equipment from in between the speakers, #2 was relocated the speakers to the get the most distance from my seating position. I previously had them wide but closer to my seating position.
So it took be a while to get to his #1; the rest I did rather quickly. My realization was that in my case #1 was an immediately noticeable improvement. But maybe primarily for my situation.
Note: another Jim suggestion was to have my subwoofers fire at the back wall. That's why they are placed on their front. If recall correctly he said I needed more travel distance for the lower sound waves.
Placement of AMP and Turntable in-between speakers
After months of denial, I bit the bullet and moved my MA352/SACD85 and Project Classic turntable to the side wall of my music room instead of placement in-between the Dynaudio Contour 20s and subs. I was encouraged by "Get Better Sound" to do so, but had already purchased shorter speaker wire lengths.
Set up is visible in my profile at the newly added photos (before/after). My conclusion was immediate; it does provide a better sound stage. More depth, more realism. I didn't think it would make that significant an impact, but for my situation it's one of the best room treatments to date.