This can be subjective as most "what is best sounding" questions. Being I am an owner of an integrated, a Levinson 383, it would be fun to compare some others on identical systems. That said, one amp may be a better match than another on a set of speakers.
I have read many claims and comments about various integrated amps, some are so far fethched to give credit, some seem to be preference and some just plain the facts.
I have recently talked with a reviewer about the Mac 6900 and the Concentra II, not about those two directly compared to one another. There was some things he didn't like on the Mac and gathered he wasn't much enthused, but was quick to mention others are. He liked the Concentra a lot, especially the build quality and parts, but did mention he liked the Plinius 8200 better.
All in all, I went away as happy as ever with my 383. I have been known in the past to get to caught up in others thoughts, I sold a 383 once, having purchased another, I will not do that hastily again; especially as I feel I have a nice synergy in my system.