Seeking best sounding El-34 tubes for my power amplifier

Pretty much depends on the sound you expect, but in the economy class of new production, inexpensive, tubes you might try JJ/Tesla which will give you a clean brighter sound or Mullards which will give a more full-range sound. Personally, I prefer the Mullards. If the JJ's, you will want to consider their E34L or the EL34. Both brands IMHO would be an improvement on the Sovteks. I have never heard these tubes on your equipment.

I like the Sovtek tubes but like the reissue Mullards the best. Enjoy those Thor amps they are really nice sounding amps. Enjoy the music

That certainly is a rare bird, I’m sure they are quite impressive. My experience with EL-34’s in other amps brought me to love the Svetlana Winged C’s, but they are pretty much gone. The other issue is what’s still available has been picked over and are new factory seconds , so expensive and unreliable. My Rogue M-180’s make 180 watts each with four power tubes. What I did with them was use new production Gold Lion KT-77’s over EL-34’s.  For me I had that desired mid range and a sturdy tube that endured being run fairly hard. In my case it’s manually biased which gave me more latitude. Although not a direct answer , but possibly helpful. Regards, Mike B. 

I really like the Electro Harmonix 6CA7's that I ran in a couple of amps.

+1 Gold Lion KT77