What would you say is THE MOST important factor to good imaging?

You don’t have to do 1/8" increments.

Image placement:
Toe out too far you start to get just a softened center image, and nothing either side of that center image.
Toe in too far and you get nothing outside the speakers, and a strong center image.

Depth perspective:
Comes from how good your speakers are, what’s between them (hopefully nothing), how far from the back wall they are

It’s all what your ear/eyes are hearing and seeing, and use a good disc that has known great imaging spread and depth. Or get a simple setup disc like the Chesky JD37, whatever you do don’t play from track 28 on wards.

Cheers George

Contrary to George’s opinion, horns can provide excellent imaging if somewhat reduced SS depth. Just another pointless dig at horns he feels he must insert. Oz

The more directional the better, that’s why esl’s, ribbons, planer ect are so good at imaging, width, depth and placement. But are usually one to two person hot spot seating, horns just have a diffused "wall of sound." 
Iv’e owned LaScala’s, Heresy’s and Forte, they don’t come close to esl’s, ribbons, planer ect.

Cheers George

mkh1099

What would you say is THE MOST important factor to good imaging?

No horns, toe in just right, stable speaker footing, nothing between the speakers, that means equipment rack/s tv ect.
Speakers should be out from the back wall, and in from the side walls.

Cheers George