I have the same amp. I've had Chinese tubes, my least favorite--don't even remember which brand they were. I've had the Sovtek's and really liked them, but had some reliability problems with them. I've had the Svetlana's, they were too soft. I'm now using Electro Harmonix, which thus far have been my favorites--very similar to the Sovteks (they may even come from the same manufacturing facility). I have been tempted to go NOS, on my phone pre-amp that made a huge difference. I did go NOS on the input tubes (RCA brown base). Tesla and Siemens are two of the EL34s I have not tried, but would like to. Perhaps others can comment on these tubes.
