I have used Svetlana and Sovtek KT88's but haven't tried the others yet. I found the Svetlana very clean and clear in the upper mids and highs (very impressively so) but a little thin in the bass and lower mid range. This was in a SF amp. I tried the Sovtek's in the same amp and was unimpressed until I changed the small tubes from Teslas to EI6dj8's - this brought the Sovteks to life and they have been in the amp in this combination for over a year now. I'm encouraged to try the EH's .......
I did not have such luck with the Svet KT88's regardless of the small tubes. I presently use Svet 6550s & JJ 6922's in my SF mono's which gives me a very balanced and detailed sound w/o excessive high end energy. Caveat - I focus on rugged tubes in my amps and have avoided some of the popular, but less reliable stuff. I hate lugging these beasts in for repairs because of a blown tube.
I did not have such luck with the Svet KT88's regardless of the small tubes. I presently use Svet 6550s & JJ 6922's in my SF mono's which gives me a very balanced and detailed sound w/o excessive high end energy. Caveat - I focus on rugged tubes in my amps and have avoided some of the popular, but less reliable stuff. I hate lugging these beasts in for repairs because of a blown tube.