Just wanted to add another endorsement for the JJ tubes. I have had my Stereomour for more than a year and put the JJ's in shortly after I received it. A couple of weeks ago, I had a problem with my goldpoint volume control and in the process of repairing it, messed up one of my tube sockets inserting a tube incorrectly.
Anyway, I ended up putting the Sovteks in and did not like the sound. Just did not sound right, very lean and a bit on the bright side of things. After fixing things and going back to the JJ's, I had a big sigh of relief. Back to the sound I love. This experience convinced me of the improvement in sound far more than any "side by side" comparison could have. Oh, FYI, I am also running an NOS Telefunken driver tube.