I thought I'd chime in here about a recent recti change that impressed me. I recently bought a NOS Dutch Philips/Amperex GZ34 for my GG2 and am very pleased. It is a fuller sound on the bottom than my EML 274b and is musical, balanced, articulate, and dynamic as hell. It took a few days to break-in and after a week, it was singing. A wow for me. I have no desire to replace it with anything at the moment because it has knitted the system together so nicely in the GG2. I know this sounds almost naive for an experienced tube user to say, but I never realized how critical the recti sets the the overall balance of the 3-legged stool with the choice of Lampi output tubes (using std KR 242 again), and choice of amplifier as the other 2 legs!
I'm sure I'll circle back to the EML 274b to validate the GZ34 one of these days, but for now, I'm in heaven with the GZ34. A few nights nights ago, it was one of those "don't want to go to sleep because the system never sounded so good". When audiophiles have nights like that, it's such a special treat because the older one gets, the rarer they seem to occur.
Hard to believe the sound that comes out of this mighty little tube, but it's certainly worth exploring and it's relatively inexpensive (about $250).
If you are considering this tube, please be aware that there are Amperex/Philips GZ34 that are Dutch made (easy to see on the date code as "K" or "L") and those make in Blackburn by Mullard ("B" in the date code). I have not yet tried the latter but both have enjoyed great reviews. (I have a Mullard on order).