I agree that an integrated, theoretically, has an advantage over separates. Not long ago, I heard a Levinson 5805 integrated playing through a pair of Magico A3 speakers at a local dealer. I fell in love with the sound from the mids on up and the holographic sound stage illusion.
I use separates but this demo sounded so good to me that I was actually seriously considering trying the 5805 in my system and Magnepans to see if it would provide these same qualities. The dealer suggested a used Levinson 326S preamp that was just traded in, basically the same preamp section the 5805 contains internally, would provide what I wanted.
I was a bit skeptical, tried it anyway, he was exactly right and I bought it. My main point is to suggest you not discount the benefit of flexibility that separates offer. I'm using the 326S stock pc and the balanced xlr cables I use are decent but nothing extravagant.
Tim