Leben CS600 owners, what tubes have you rolled?

Do yourself a favor and purchase the Reflector 6n3ce tubes from Jim McShane. Read Jeff Day's review blog of all the tubes he's rolled. Day writes o 6Moons and Positive Feedback. My brother has this amp and it sounds great. The tubes above is what he settled on.

Neil,
On my setup, the Reflector 6n3ce tubes are very well balanced tonally and are the exact replacement for the 6L6GC as far as setting go. If you are using Sovteks now you will notice a much more smoother treble and midrange and the same bass slam as you are used to.
I have heard the SED 6L6GC and not the RCA black plates and the reflector is far better.For the price the reflector option seems like a very good bet as they are not expensive..you can always keep it as a backup.

Another option is the Tung Sol KT120. I still am awaiting mine to roll to see the difference but they are supposed to be much better (let me check to see where it is better and by how much)

The power difference will be quite large between the 6n3ce and the KT-120. Not even close. I wonder if a reasonable comparison can be done under such circumstances.