Soundstage

Don't know where this equilateral triangle deal came from but it is erroneous.  

Speaker setup is a two-step process. 

Step one, move them around relative to the walls listening for bass balance and tone. Listener position matters as much as speaker location so listen to each speaker location from closer and further away. Step One the speakers do not need to be perfectly equidistant or symmetrical, but pretty close. 

Step Two, now from the smoothest sounding location measure very accurately to get them perfectly equidistant and symmetrical. Listen for image focus and sound stage width and depth. Adjust the toe in very slightly and the image focus and depth will be greater. Adjust the toe out very slightly and the sound stage width will expand. Equidistance and symmetry must be precise each and every time or you will lose image focus and think it was due to changing toe when really it was sloppy symmetry. 

When you are happy with the balance you are done. Does not matter what the distances are. That is all simplified to the point of rubbish. This is how you do it. 

Interesting post Duke. Because some of the most enthusiastic comments on my system have to do with superb image focus and a stage that extends beyond the speakers. My feeling for some time now has been more you are there than they are here. My room, in other words, disappears. The untreated (well, HFT) side walls do not seem to interfere with rock solid imaging. Each record is not only a different sound, it is a different world. Some you are right in it, others it is further away, some it is rather flat, still others it extends deep and wide.

This is actually one of the hardest things to get across to people, because there is a tendency to assume what you are hearing is the system. The more that is the case the easier it is to evaluate. But the more the system disappears the harder this becomes. Depending on what I play you could leave convinced my system is flat and narrow, or deep and wide, but only a great deal of time listening to a wide range of music will reveal the truth, that it was the recordings not the system.  

I suspect this is because as important as the speakers and the room are, still they are but two on a very long list of things that matter.

Had to read the OP a couple times to make sense of it. The sound stage is narrow- but extends beyond the speakers. Okay, that is not narrow. The sound stage is detailed and precise but not deep. Well that is largely down to the recording. A lot of them are just about as you describe. Some further forward, some with greater depth front to back. They are all over the map. 

These are horns we are talking about. Not a big horn fan, you will have to ask someone who actually used your speakers to know for sure what they are capable of in this area. Also a lot of things like Townshend Podiums and Pods, Synergistic HFT, etc will make big improvements in all the areas you are looking for. Whatever you do, do NOT go multichannel, you will find yourself immersed in pure dreck.