To me, the tubes do have subtle differences in sound rendering. As I mentioned above in a prior post, the Miniwatts sounded a tiny bit brighter than the Amperex. My preference is for a intimate club sound, not a bright space. The Amperex, so far, are perfect for me: when listening, I simply stop thinking about the hardware and bit streams and just get lost in the music... Any tube that is so "easy listening" is one for me.
Now I am trying a pair of Reflector grey shields, then will get around to a pair of Telefunken Cca, then maybe I will find time to break in, listen and write up the GE5670's that iFi flogs in a 6922 adapter.