I agree about the Mastersound, but the S6, I had one for a while, whilst my main amp was going through a long repair, I thought it was frankly poor. I found it soft, lacking in detail and tonality. Maybe it was just my system.
Now Ayon make wonderful amps and I don't know why they don't get more recognition. I compared the Orion to the similarly priced Spark and if you can manage on 20 watts, which you should do with Zu, it is clearly a better amp. Lovely rich, but detailed tone, good frequency extremes for a tube amp. I prefered it to the much repected Viva Solista, I used for 4 years.