Mapman,
I'm not a professional reviewer, but as the great film director, William Wyler once said when asked, what he wanted, from a particular actor after about 40 takes, he said, "I'll know it when I see it. I think this is the correct response to your question, only change it to "you'll know the difference when you hear it for yourself.
By the way, my unit was bought used and did not come with the stock rectifier tube. It arced over and the original owner replaced it with Kevin Deal recommended NOS Phillips ST bottle 5R4GYS. Nice tube but not recommended for this unit by Israel Blume. With this rectifier in the amp it sounded brighter, my wife did not like the tone of the bass, the sound was less warm, lean and thinner. Nor did she or I like the Gold Lion KT77s that the previous owner had installed paired with the Phillips rectifier and stock 6SL7s. I will revisit the GL KT77s with the Mullard rectifier as well as the Sylvania military 6SL7. Should be fun and interesting. First I'm going to test out the RFT Siemens and Black Treasures, then the SED Winged C at a later date.
