You may think I'm 100% on tube amps. Not correct. On several occasions I've heard the A21+'s big brother (Halo JC5) pared with Manley Steelhead and I was mightily impressed. Why would the A21+ do less except for power rating?
I took my chances and ordered the A21+ and so far I'm more than pleased with the performance run from my EAR-868PL/EAR-MC4 and my EAR-912 preamps.
What made it an obvious choice was also that it has the same features as my beloved EAR-861, variable gain and balanced input to name a few. In addition to this more than 10 times the power whenever I need a rock-solid power horse for less efficient speakers. That said, it works very well with high-efficiency speakers too. It may not have the slightly more forward and holographic midrange of the EAR-861, but basically it's just another way of presenting the soundstage. There is certainly no lack of transparency as such, only - possibly - a more neutral presentation.
The reason for taking on the A21+ is also plans for a seriously large speaker, possibly in 2025, but time will tell. Said speaker may well do 95 dB sensitivity, but huge bass drivers requires massive power despite high efficiency.
Actually the A21+ was measured to 400 wpc by Stereophile.

Below pics nicked from the Parasound website.