I totally forgot about this thread, but since Mozartfan revived it, here goes my follow up:
Some time after I started this thread, I went to audition the Cayin 300B. Didn't like it. Like all Cayin products, the amplifier was gorgeous and very well built, a work of art! But I found the sound to be lazy and too warm; sluggish. Was missing some spark, some crispiness - for my taste.
By the same time I also auditioned some amplifiers from Line Magnetic and my choice was clear, my favourite one was the LM 805 ia. I really like everything about this amplifier, especially the sound. And I was almost pulling the trigger when a fantastic deal came around: I got the bigger sibling, the LM 219ia for half the regular price. Even though this huge beast wasn't my favourite, I couldn't let it pass. So I bought it and I was very happy for some time. Until I discovered a very small, low powered push-pull amplifier developed by a friend of mine: the KA-101 from Kingko Audio.
Kingko Audio is owned by King Ip, a good friend of mine from Hong Kong. He used to sell and repair amplifiers from Line Magnetic and he knows everything about audio electronics and tubes. So after years of studying other brands, he developed a small and simple product, not expensive, that rivals in sound. It is a giant slayer!
I bought one, together with his CD player (also using tubes) and it sounds as good as the best Cayin and Line Magnetic. Actually, is almost as good as an Audio Note, or a Shindo! We spent days comparing them, with a lot of different speakers. The little Kingko KA-101 surprised and amazed everybody.
Soon after I sold the LM219ia. And I don't feel the need to search anymore for a good SET, I'm happy with my Cayin MT45-Mk2 and this Kingko. For now... :)