Kora Hermes- What valves do owners recommend?

After a long wait I have finally received my Hermes and its sound is wonderful! I am curious to know what valves other owners are using. At present mine has the stock Sovteks but a number of users have commented that their are better valves that will improve its performance.
Any opinions would be greatly appreciated!
I prefer the Tesla tubes over Sovtek.
I am thoroughly enjoying some Mullard CV2493 gold pin tubes in both my Hermes and Eclipse. Wonderful body, air holographic imaging and smoothness while still offering gobs of bass, nuance, detail and high and extension. They really add to the Kora gears ability to bring the essence of the music alive. To be fair though I've only compared them to the Sovteks.
I replaced the stock units in mine with Telefunken Falcons. Huge difference in sound - My other choice would have been the Siemens.
We really like the following tubes in the Hermes. Siemens CCa or 7308's. Telefunken Falcon Grade. All are outstanding. Hope this helps.
My Hermes came with Phillips tubes installed. I've only had the DAC two months, but during that time I've collected Siemens CCas, Siemens E88CCs, Tungsrams and Mullards. I just swapped the CCas in this past weekend and am letting them burn in, but I get the feeling I'll be like Sjberg and favor the warmer Mullards. Maxie, it's a great DAC isn't it?
Sovteks are aceptable (IMO), if you run all tubes (Pre-amp and amps). Otherwise, I agree with previous posts (Amperex, Mullards, Telefunken, Siemens.
Thanks to all of you for your opinions / advice. I am very grateful to others with first hand experience taking the time to help me out. As is always the case, one must use ones own ears in making a decision regarding equipment, but it pays to listen to any advice offered.