Cdente, I really tried them. I find the sound harsh. I even tried the VB1s with the amp's 4 ohm taps which should have offset some of the brightness I reported above. Still harsh, even hurt my ears a little.
If I didn't know better, I thought I heard some type of sibilance or distortion coming off the right channel. But that's just me. I checked the amp's tubes and all is ok.
I sent an e mail to ARC to get the official reaction, which may be just be, "no opinion at all."
If there are any other ARC tube amp owners out there who have tried the VB1s, I'd sure like to read their comments.
And I will check Audiocircle as you suggest.
Thanks for the tip. Nothing ventured, nothing gained.