Thanks, I've taken that approach already. The drivers aren't blown, but it wouldn't likely happen on three speaker systems, in any case. And I have several amps, several speaker systems.
However, since then, the harshness seems to have gone, which leads me to the conclusion that something in the system (either the Valkyrja or the First Sound) were not fully broken in. Unfortunately, I cannot determine which one was the culprit. I left the room, with music playing, returned an hour later, and no only was the harshness gone, but the sound had transformed, like Cinderella after the Fairy Godmother waved her wand.
The instruments were actually larger and the musical lines were much better. Instruments had body to them, and the stage itself was vastly larger than before.
All this over the course of an hour?!?!
I just wish I could pinpoint which component was the culprit originally. The First Sound Presence Deluxe Mk II had only arrived in my home 10 days ago and I was still breaking it in, although Emanuel Go suggested that it would be broken in after a week. However, he did, in response to my question, indicate that the volume used for break-in was a factor. I had kept the volume at normal conversational levels due to an ailing parent, so perhaps it hadn't fully settled in.
The Valkyrja arrived around the same time, and I don't know about its break in time. Since I bought it on Audiogon through a dealer, and the dealer didn't know how long the previous customer had spent breaking it in, it's possible that the cable was responsible. Roy Gregory, in HiFi+, indicated that the Valkyrja took around 400 hours to break in. However, a call to Nordost yesterday got a response of around 100 hours to break in. Who to believe, Gregory or Nordost??
Things sound heartbreakingly moving now, so all's well that ends well. A belated Christmas present, but one I'm happy to have received!