I am using some different tubes...I switch back and forth...but for 12AU7's I'm using Mullards. 12AX7's I'm using Telefunkens, and for the Phono section I'm using some Russian tubes...can't remember the designation right now...but they are EXPENSIVE....also using 6DJ7's and they are NOS JAN Sylvania....a very nice tube...
I love to roll tubes...one of the main reasons to own a tube amp or pre...tube rolling.. Blindfolded, I don't know if I could HEAR the difference in Chinese and high dollar NOS Vintage though..gets back to the psychacousic theory I have...I think a lot of something "sounding better" has do so with your expectations...or the recommendations of others...