lozoyad, I think three or four things are at work here.
Regardless of speaker, imaging is probably going to improve by pulling the stands out. I've gotten significantly different results in different rooms, even using the identical system and sources. This could end up in hours of tuning for you, but when you find the sweet spot I think anything you place in it will open up even more. I think Buford is onto something here.
Second, toe is critical. The planar tweeter has somewhat tighter directivity than average and does not broadcast the presence region as widely as a conventional dome tweeter typically does. There are pros and cons to this, but in general you'll get the harmonic and spatial balance both aligned when you toe the A1b so you can just see the inside walls of the cabinet from your chair. About halfway between square to the room and aimed right at you is preferred - Buford is right. Too wide and the image doesn't develop and too narrow and you can locate the speakers at the same time they become brighter. Less then a degree can make a big difference - I spend nearly as much time on this as I do geographical room placement.
Third, every multiway will come into better harmonic and spatial focus when you also achieve the proper vertical angle. If you're not already, try tipping the A1bs back so that while listening you are perpendicular to about the mid point on the front baffle. The planar tweeter is taller than average and you can miss important information if you're too far above its axis. Tuning this together with toe may very well be most of the trick here.
Lastly, the A1b's tuning, as I think you discovered already, favors a black, quiet background. This owes to the tweeter's larger surface area and correspondingly lower distortion as well as Arx's general sonic personality. Just as you may find it harder to localize each speaker when well established in the front stage per the above, it's the speaker's nature to reduce hifi artifacts that can sensationalize the sound. Even the ~40kHz dome tweeter in the Danas have somewhat more presence, although the Arx tweeter I think just has less overall personality in the crossover region. Good alignment relative to your seated position will optimize the highs, but they're not going to sound identical to a dome tweeter.
Overall, I'd encourage you to align angles and to reposition your stands out further in the room. Whether you wish to leave the speakers in such a position when you're done is up to you, but as en exercise I'm betting position and alignment are the missing elements.
Chane Music & Cinema