I first have to say that for those who want to take this with a grain of salt, so be it - I'm a part of Fried Products...
However, luckily, before he died, Bud Fried gave me his longtime personal loudspeakers - C/4 satellites with O subwoofers, and they are without a doubt the best imaging speakers I have EVER been around. Of course, they are a one off pair, and all of the drivers were custom built to his own specification. And, the crossovers were tweaked and tweaked and tweaked until it sounded right to him.
I used to think it was the time alignment/minimum baffle of the truncated pyramids that are the C sats, but experience has proven to me that the REAL secret is the series crossover. A close friend and I talk a lot, and through experimentation the series crossover just provides such superior imaging that it's flat out uncanny. At one juncture, while I was listening, I jumped up because I heard the phone ringing several yards behind me - it was the music! And, my listening position is right up against the back wall. Talk about one of those jaw dropping moments - I was flat out dumbfounded!