I find with the herron that you really don't need to go crazy on vintage Tubes. Keith has done an excellent job voicing it with the Tubes he provides.That has been my feeling as well. While in the case of various tube power amps I have used over the years I have found small signal tubes to make dramatic differences, and in most applications I have found tubes from the 1940s to 1960s to be preferable to recent production, I have never felt any desire to tinker with the voicing Keith has achieved with the tubes he supplies in his phono stage.
Best regards,
-- Al