This subject is wearing on me and this comment may be a sign of that but at the end of the day there is no evolution, no advancement of the state of the art to be had with tube amps. There is little left after gimmicks, convenience, and reliability. "Whither Audio Research" is a very clever title but can just as aptly used with "Whither Conrad-Johnson" or "Whither Manley Labs" (which credit to EveAnna does not mess with proven designs and does not play the "SE" and successive number game) or "Whither Lamm" or "Whither BAT" game. I say all this as someone who always longed for ARC and eventually, and with little regret, went all-in with ARC. I have little regret too.
Amps do sound different from one another and no perfect amp exists. I always think of Charley Hansen who only towards the end of his far-too-short life discovered that tubes do offer a magic not normally achieved with SS gear.
Like it or not this hobby of ours has a commercial industry side to it and like it or not the commercial side thrives on selling what is largely slight of hand, perception-over-reality, sell the sizzle and not the steak illusions. And.....the audio press is all too happy to dispense the news of the illusion like so many doctors selling what the pharmaceutical rep pushes.
I sense a wave toward solid state gear like CH Precision, DaRTzeel, Pilium and similar capturing the confidence game that is part and parcel of so-called critical listening over the next 6-10 years. I sense this just from going to shows and reading the press. There are many factors involved including perceived technological advances combined with ease of maintenance. As the audiophiles with money to spend slide over to a previous segment of aging demographics there are less and less inclined to believe in the "magic of tubes" or to be willing to spend time with equipment failure or maintenance.
I suspect Ralph Karsten saw this coming when he decided to advance Class D gear and he is not alone.
So yes, the much vaunted Audio Research Corporation has faced a perfect storm of adverse elements-inflation, supply chain issues, lower priced competition, a market shift away from tubed gear, and dare I say it, less consumer based adoption of the magic myth and mystery (alliteration intended) in tubes.