Try asking the Manley folks. I understand they will take the time to talk to you.
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For the EL84, this tube is also 6BQ6 and 7320. Best ever is the Telefunken if you can find them. Then a three way tie with Siemens, Dutch Amperex and Mullard.
For USA 6BQ6, late 1950s RCA black plates are excellent and likely one third the price of Telefunken's.
The 6414, I have no personal experience with these but have heard that the old Raytheon is a good tube, much better than currently manufactured stocks.
The 12AT-7 is easy, Telefunken. If you cannot find Telefunken, the Amperex 7316 is excellent with great dynamics and (usually) very quiet. Good luck with your tube rolling.