The airiness and that sense of each instrument having own space is superlative in Phantom. It was similar to that wow effect when you hear the a great planar speakers for the first time, going from a low end cone speakers.
I work a lot on my iPad while listening to music. Many times, I would spontaneous look up to peek at the musicians, just out of reflex. Talk about feeling like "being there"...
But I did have great fun listening to Ref5se. It adds a bit of excitement to music, especially at the top end. And you can't beat that midrange tube magic. The bottom end was exceptionally well controlled even compared to solid state gear. The soundstage was great, but here is where Phantom trumps it.
And this is the strange part, Phantom didn't have that slight harshness that ref5se exhibited on some recordings. Apexorca on another thread mentioned this and I had my doubts. Not any more
I bet if I pair Krell 302e (or 400e) & ARC ref5se with Martin Logan CLX, I may get that sense of airiness and soundstage. But I wouldn't get that tight control from low midrange and down.
I agree Krells can sometimes sound too "real" and it can sound a bit analytical. I like that kind of sound. So, only your ears can decide.
BTW, what speakers do you have?