My monos came with the SED Winge3d C 34s... I bought another matched set from AES in Az. I do like 'em a lot.
I've found the mini tubes (3 per block) do more for or to, the sound. As do tube rings there as well. On mine, I can mix these 3 tubes up, as long as the bottom of the triangle of tube (first stage output?) remain the same types.
The combinations and resultant sonic choices are plentiful. Primarily in terms of sound stage, speed and resolution though, not so much by way of timber.
Enjoy.