As a former speaker manufacturer, I have listened to many, many amps and I have always liked the Sudgen sound. Clean, pure, sweet, natural. For that matter, I like Class A amps. The FPA4, discontinued in 2019, was based on the A21, so you have some very good DNA there. But is is not the same as the A21SE. The XA25 is unlike other Pass amps, so you need to hear it to appreciate what it is. It has its own sound and is close to a single ended tube sound. It is actually the one Pass amp that I like the best. Read Teajays's and the others review. I have 4 favorite ss amps and the XA25 is one, which I also own. It comes down to your ears and what is in the rest of your system. But there is something special and just right about the XA25. I hope you can find some way to compare them side by side.
