I owned the original V12 about 10 years ago. Of the tubes I tried, I thought the EH 6CA7 worked the best. Contrary to some, I didn't like the Svetlana SED KT88; they were very closed in on the top (no pop).
I would suggest talking to Kevin Deal at Upscale Audio. He used to sell Cary. I think he liked the new Mullard EL34, among other options. I would also suggest upgrading the other tubes. Mine used 6922s and changing those-- to NOS Siemens-- made a big difference. He could probably help you here, too.
I would suggest talking to Kevin Deal at Upscale Audio. He used to sell Cary. I think he liked the new Mullard EL34, among other options. I would also suggest upgrading the other tubes. Mine used 6922s and changing those-- to NOS Siemens-- made a big difference. He could probably help you here, too.