amongst old stock alternatives
1) the gold lion genalec gec kt77’s were viewed as the best... superb all around
2) followed by the mullard or amperex british or dutch made el34’s, also superb slightly weaker in bass but palpable and refined
3) third best were japan made matsushita el34’s with seam top, these were made on mullard tooling moved to japan after mullard ceased production in the uk, lovely spotlit voices and imaging
4) svetlana el34’s were next best (winged c st pete factory), beautiful balance, a little less refined
5) siemens telefunken skinny body el34’s with dimple top ... somewhat lean in character but clear and precise
6) usa made ge or sylvania fat boy 6ca7’s next (somewhat rolled off)
the above are probably cost prohibitive in an amp set up needing many multiples of these though
probably best to use what is available from upscale in terms of modern tubes but even then tube supply from russia is curtailed these days, so you are looking at jj/czech or chinese alternatives
note that modern day versions of gold lions mullards and so on are all russian made... not necessarily bad tubes but they are not the real deal from the 60's-70's-80's from first world western europe and so on