Quote: it might be a bad tube because I don't think even brand new out of the box a Amperex 6922 would sound muddy and way too warm.
I'm thinking that it's probably a bad tube for the same reason. I had to look through the raft of PCC88's, TF PCC189, Siemens E88CC of particular vintage etc, etc, etc that I still have but do not use. I had a NOS Amprex BB which I don't know what happened to, but it was not muddy although not my favourite in the UFO. One of my favourites was an ADZAM E188CC SQ quality.
I would try another tube.