I welcome input from anyone familar with the captioned amps to assist in evaluating their differences, could not locate any published reviews on them. A Prima Luna Prologue 3 with upgraded tubes is the preamp.
I would go with the McIntosh any day over Krell. The McIntosh equipment has more feeling and emotion to it. If that makes any since at all? The Krell just sounds like someone was playing your favorite song but with a heavy blanket in between you and the speaker. I had the opportunity just yesterday to listen to the pair you are talking about. I also like the looks of the McIntosh equipment far better.
Agree on the visual aspect. From your comment I draw the conclusion that the Krell seems "sterile" to you and the Mac more involving. Care to ID the speakers you heard these amps drive?
This is like comparing apples and roofing nails. They almost nothing in common! I can't imagine anyone really liking both, as they are soooo different in tonal feel, perspective, presentation, and application. Even within their specific brand structures, the MAC being an homage to both their past and amplifier design generally, whereas the Krell is an entry-level high-end, high power amp.
So TA I presume the Mac is the Apple and Krell roofing nails? Impossible for me to compare side by side, nor by similar speaker(s). Hence my reason for seeking input from other audio hobbyists.