A horn speaker placed in a corner will lack wall reflections that give a sense of depth. Horns are more directional than other kinds of drivers, so the only depth you will hear is that which is in the recording.
There are pros and cons to every aspect of speaker design. Room reflection is just another variable. It seems to me that I have heard a nice spread of image from k-horns before. It was a long time ago, but I was very impressed by them. I use Forte IIs, not in corners. They have a wide image and some depth, but not with precision of my Swans or PMCs, but the music does have a "live" feel. My Alons present in their own distinct way. Add the fact that different amps change the presentation...
There are pros and cons to every aspect of speaker design. Room reflection is just another variable. It seems to me that I have heard a nice spread of image from k-horns before. It was a long time ago, but I was very impressed by them. I use Forte IIs, not in corners. They have a wide image and some depth, but not with precision of my Swans or PMCs, but the music does have a "live" feel. My Alons present in their own distinct way. Add the fact that different amps change the presentation...