Suggestions please. Your favorite 3, 12ax7 tubes

Hi, thanks for any suggestions. Looking to purchase 2 or 3 pair of 12ax7’s for a Audio Hungary a50i. Right now I’m using Mullard 1960’s Blackburn and have Gold lion gold pin as back ups.
 

I’m considering the Telefunken but don’t want bright or sterile or it to shout at me, but still very interested due to there reputation. I hear the RCA black plates are nice. I have always liked the RCA 6sn7’s but not sure if they sound close to each other. Another one I was considering is the Tungsram, not much experience with 12ax7’s so any insight would be appreciated.