Sugden has been building the A21 for like 40 something years! If you have doubts about the quality, then I’d advise you to read all the positive reviews on the A21 SE signature pure class A integrated. Better yet, seek one out to listen to. To me, it is a fantastic match for the Tannoys. Guess you would also frown upon some of the class A products from Pass?
I'm not frowning on things. I just feel like I have a great all-round amp, already, in the 152, which has plenty of power. If I were going to spend more money on amplification right now, it would be to get something that's more of a "specialist." Something that really does one thing -- like soundstaging, for example -- spectacularly well.