EL34 & 6L6 characteristics

You may find that the small (voltage amplifier and driver) tubes in the amp make a bigger difference than the power tubes, assuming that the power tubes are good when compared.

I agree Atmasphere .
But I really found a pleasing and significant difference with the 6Ca7's . With these I am most of the way there and hopefully don't have to spend a bunch for NOS tubes to make bigger changes .
For instance...I have been working with some KT-120's that I find quite pleasing in the extremes but quite lacking in the all important midrange . Rolling all of the usual small tubes has shown me that I preferred the Amperex sound . Now I will try the better Amperex trying to get the little bit that was missing with the lesser grade Amperex's that I was experimenting with .
With these 6CA7's , I may be able to get to the same place with some much less expensive Cifte or some Spanish 12AU7 variants to get the sparkle and top end increase that I am looking for .
It's all about the infinite possibilities available and trying to find that right combination . And maybe pick up a little education along the way !

Cifte is a good tube very much a tube with very good highs. Do you use this tube? Are you looking for a pair?

I use PL mono amps in one system. There are definitely a lot of shadings possible when tube rolling the PL amps, so I understand the desire to find that optimal trade-off. I'm not sure that it's possible, but I ended up settling on Tung-sol KT-66 tubes in my system. Not quite as warm as EL 34, but the bass is tightened up a bit. The sound struck me as slightly warmer than the kt-88, so I felt that this was the best trade-off for my taste.

FWIW

Ryriken66 ;
I just ordered a pair yesterday .

Martykl ;
What are you using for a preamp ? If it has tubes , what are they ?