For me Riviera amp is the best,and his designer;luca Chiomenti,is one of the best.Imai,owner of Audiotekne,told me that Chiomenti is the only one that knows how to do output transformer for tube amp.
Chiomenti produce also with other company ha has KIOM,very special tube amp and horn speaker.
He went in my home in 1994 to listen my system full Audiotekne nd we have a very good relationship