I don't agree at all with the term "silky treble" to characterize the 400xi. Unless you have a silk-dome tweeter of course, then maybe you would hear that tonality. But thats not this integrated you would be hearing. Usually thats a term I would associate with tube equipment, and a few select SS integrateds; the treble here for the 400xi is well-defined, the mid-range is decent, transparency is there, fairly dark backgrounds. Overall presentation is typical Krell, dynamic, big and honest, lively, good to excellent bass control.
If I were looking for 'silky' highs, I certainly would not look to this piece for it. Overall this piece is a nice entry level, and an incredible value, and does all sorts of music pretty well. But I find it to be a little sterile and analytical for longer periods of listening, with little to no emotional/musical involvement. However most people looking for an integrated in this range may not be looking for emotional involvement.