Hi Serge,
I have audition my Leben CS300XS, before the mods and AFTER the mods. I like the AFTER better as it had much more.
Back to your question: How does it sound?
As a standard piece, it sound fluid, smooth and POWERFUL, give that its only a 15 watts amp. More so, driving the Duevel Planets where its not tube friendly in any way. Yet the sound it produces is very so very nice. I dont know how to describe sound, but for sure, one can keep listening to it and one can never fault it.
Of course, my mod piece is even better, in every way. Hordes of customers came in listening to my amp (being run in - due to the component changes) and everyone can only said one word ... unbelievable, for the price and performance. In fact, they thought it was the Air Tight Pre/Power amps in play. And my friend bought one and have it brought up to the same exact level .. of course paying premium as he had it new (mine used). 2 words best describe - VERY MUSICAL!
So my dear friend, get one. Its worth every cent. I did the mod because I bought it used and with the difference in dollars between a new and used (some 30%), I used the cash difference to soup up the amp and my, what a change! You will love it! Small, exquisitely build, and very musical!
I can only used these words to best describe the Leben - Its smooth, lucid and palpable. And in a way powerful too! Matched with the right efficient speakers, its every bit as good as any top tube amplifiers. This statement comes from my local dealer and I believe him as he had in his line - Air Tight, Reimyo, AMR and Kondo. Last but not least, its really "value for money" for what it gives.
Sadly, I had also bought the amp knowing I will never be ale to use it for a while. So its now sitting on top of my CD cabinet besides the pot of flowers. And know what, its been discovered by my wife. She did not kick up and fuss but merely told me: Are you keeping that for John (my friend) or did you buy it for yourself?
I just kept quiet and mumbled .... for eh .... John .... but its really mine. I dont know she heard the last words or not, but for sure, she did not say anything about it this morning on the way to work.