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

Experience has taught me that hardware is critical, but of course so are the room/treatments, the speakers themselves,and the recording's engineering/mastering quality.

But I would have to say that the biggest influence is the room, with speakers and mastering a close second...

What do you say?

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Until recently, I would have said the right speaker with the right room treatment and speaker position. The right components that provide the finest resolution possible.

Then recently I discovered just how much cables can effect imaging.

The size of the image, placement of performers within the image and the amount of space between performers were significantly improved by using great cables. And I mean all cables - interconnects, speaker AND power cables.

Cables allow the entire system to reproduce the smallest details, like the echoes and reverberations within the venue that provide the sense of space within the venue itself and ultimately the reality of live concerts.

Cables will even allow modestly price components to excel and sound amazing

Just my five cents worth - Steve :-)
Agree with everything mentioned above (even roberjerman). In addition I would add control of micro-vibrations via feet, racks, weight (on top of components), etc. It all makes a difference. 
Obviously everything matters but number one on my list would be speaker placement.
Speaker placement, but you have to have a room that allows a good placement. While I've been able to achieve excellent horizontal image placement and a very wide sound stage in a small room, getting great depth has, for me, required that speakers be positioned more than a couple feet from the front wall. Six or seven feet into the room works very well. I've also found that dipole speakers (planars or open baffle) tend to provide more image depth than monopoles. 
The quality of your A/C and the lowest noise-floor electronics you can afford.
AC power for sure, but tops is speaker placement. Makes all the difference. 
IMO a dedicated/treated audio room is tops. Given this, you have the latitude to place you speakers properly for best imaging as well as your seat.

Next, the speaker itself. Most speakers can image well if given the chance, but some do this much better than others.

Next comes the electronics and accessories.
What would you say is THE MOST important factor to good imaging?

That’s easy. The speakers must be connected in phase.
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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
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.

Another vital factor is the quality of your hearing. If the sensitivity and frequency detection of your ears is different, your brain can’t optimally decode and place images in their proper place. I know from personal experience.
"Balance control knob"  

Don't laugh. It's not funny - not when employed properly. 

Stay tuned for my latest review at Dagogo.com, in which I discuss a fascinating speaker system that allows, among other things, for very precise manipulation of the center image via controlling left and right speakers. 

I also had yet another unusual and highly efficacious feature of the Legacy Audio Valor and Wavelet System (Besides L/R centering) that allowed contouring the center image to give the impression of moving the listening chair closer or further from the performance, like an adjustment from "front hall" all the way to "back hall". I sorely miss that feature, because it was compelling!  (Also reviewed for Dagogo.com)
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
Well that's that then... Let it be known horns do not image (looking for gavel to hit table)
#1 would be getting rid of all reflections in the room . Obviously not all . Third wall reflections and on will not have much energy anyways . Try it out . Buy some Owens Corning or Johnsmanville 2'x4' rigid insulation as a test in your room . Under $100 for a 9 sheet pack where I live. Buy 9,18,27 sheets . Do your testing . Keep the stuff or buy professionally . I have moved a few times recently and listed hundreds of sheets on craigslist and sold it everytime I listed it at 3/4 of its retail . 
Program material/mastering. If it’s not there, no speaker placement, no cables, no room treatments, no electronics will create it or correct it or enhance it.
Some of the best imaging setups I have heard, the speakers were extremely far out into the room, as in dedicated listening space.

I keep my TAD’S on the long wall, almost five feet into the room (measured from the rear) since it’s not a dedicated room and can’t afford more space behind without making the listening distance too close.

The benefit of this setup is having them close to 10’ from the side walls.

When I first purchased the loft space, was planning on placing them on the short wall to allow a little more space behind the speaker, and a more distant listening position.

However, I had THE Andrew Jones look at the raw space before I moved in and he suggest the long wall setup, and I who am I to argue with a trained physicist. 
 horns just have a diffused "wall of sound." 

Utter nonsense. If you can’t get horns to image, you are doing something wrong. And horns are a lot more directional than planars. You are very confused.

Utter nonsense. If you can’t get horns to image, you are doing something wrong. And horns are a lot more directional than planars.
You are very confused.

Amen to that Ozzy.
There is only one , get everything right  . You can get a decent system  from the buy and try necessity for about 100 K .
@douglas_schroeder ....the Legacys' have all the means to accomplish 'what they do' with the room correction, the amt tweeters, and it's other details.....

I've accomplished basically the same for +/- 2% of their price.

The rest of the $ I'll apply to my speakers...;)

As is said: "Priceless."

...and I agree with Wolfie62....if it's not in the mastering, you can't fix it.

'Pig's ear>Silk Purse' still doesn't exist....

Yours Conceptually, J
The weakest link.
You can’t answer this absolutely without context. There are multiple conditions that are necessary without being individually sufficient. You have a series of elements aimed at producing a desired outcome. If any of them are inadequate the outcome will suffer. A perfect hardware chain from power to room acoustics would be useless with a mono recording. 
assuming excellent engineering of source material, any decent system, and decent speakers:

speaker placement in a room with not too close side and rear walls to avoid too early reflections, listening position close to equal distance triangle, adjust toe in direct for center only, or adjust toe in for a bit wider imaging for 2 focused listeners, (thus: method of moving/marking speaker locations tto change to either situation) and,

balance control, remote from listening position, to instantly fix darn good but not perfect engineering/balance for any individual track, live broadcast, whole 'collection' lps, cds ... with a gaggle of different tracks involving different engineering.
avsjerry, what’s your point? Are you suggesting you are getting anything remotely close to the sound of the Valor with 2% of the budget?

Why don’t you detail your system here? How about posting it entirely, including cabling. Further, you have shown you can post pics. I would like to see images of your system and room.

You made big claims. How about trying to back it up? :)

Now, if you meant getting somewhat, or "basically" the same in one parameter of performance, I still would question that for several reasons, but at least it would be a comment made in the realm of possibility and sensibility.  
ozzy62, what's your problem? I'm entitled to doubt claims that seem incredulous. He mentions the Legacy Valor speakers I first commented about, then says he has accomplished, "I've accomplished basically the same for +/- 2% of their price."  

Now, let's look at that claim, which, if it pertains to holistic sound, means he claims he is getting the same sound from about +/- $1,600 investment. Does he mean the DAC, processor, preamp all included, because that would necessarily be the need in order to substantiate such a claim, as the Legacy Wavelet combines all these. This also, imo, would be a nonsensical claim. 

Does he mean he thinks he is getting the speakers to sound like the Valor? Does he think he's going to get sound quality anywhere near it if he uses +/- $1,600 on gear? 

So, yeah, I want clarification. I pointed out that he may be discussing merely one parameter, that is, center imaging. Frankly, with his speakers shown he is not getting anything remotely like the Valor in terms of imaging. I know that because I own omni speakers and am familiar with the dispersion pattern. 

I never knew good imaging in my room until DIY room treatments - first reflection points and bass traps on the front wall.  Instant huge improvement, even with my very modest system.  Are treatments the biggest influence?  In my experience maybe.  But of course everything matters.  I agree that the recording has a great deal to do with it. A flat/dead recording will probably never image well.  Also, I still enjoy listening to occasional metal but I never really get good imaging as with other genres.
catdoorman  seems to imply that mono recordings don’t image well or not at all.  I believe that is not true.  Sure they don’t throw instruments from side to side across the stage, but most of my mono recordings, especially vintage recordings present a big, rock solid believable image that I find very satisfying.  Julie London sounds like she is in the room.  In fact, my most expensive cartridge is mono to service a large mono collection.  Anyone else like this?
best speaker position for start, synergy with power amp follows, when everything is optimised including cabling for signal & power things will be more in focus. If you want to dig further any decent room tratment will make them dissapear.
Big part is the recording. Other components having superior phase characteristics.
Since you have to get everything right , hard to say .
Try toe in every 1/ 8th inch over a week or 2 .
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
Of course you don't have to but in last  50 years has worked best for me.
Of course that's only on acoustic music  aka jazz and classical .
With rock why bother .