Audible illusions Modulus 3A or Klyne 6L

I've owned numerous Modulus preamps including a M3, 3 - M3a's, a L-1 and a L-2. I have never had tube issues with any of them. If you ignore the advice of AI and others about certain NOS tubes, yes, you will have an issue but this is your on fault for putting those tubes in them. Use regular, graded, low noise Electro Harmonix or Russian type III tubes and you're fine.
I just changed a set of tubes in a M3A that I know had been in it for over 2 years with no trouble until just recently when one became noisy until warmed up an hour or so. (This preamp was one of the first M3a's built in 1995. It does not have the stepped volume controls. It is by far my favorite of the bunch.)
I am not familiar with the Klyne and to be honest, have never read anything about it one way or the other so I'm not getting into the which is better (better is in the ears of the listener anyway.)
I can say that the Modulus 3 series has a wonderful reputation and is a great sounding preamp, especially for the money. There's not but so many ways you can design a tube preamp. AI's design is definitely one of the best still. It's designed for sonic purity and that is certainly not everyones cup of tea. It doesn't sound particularly tubey. Not using a cathode follower is tough on certain tubes but as I have found, no more so than some other high dollar preamps I've had around and compared it to. Is it perfect-no. Is it going to get in the way of musical enjoyment-absolutely not.

This post is a little late but Aesthetix had issues with their 12AX7's in the Calypso preamp. It ate them for lunch and I should know. I spent enough on replacement tubes. However, it you finally got a good pair, it was wonderful. Jim White is a very good designer and easy to talk. I think he builds excellent equipment but it does have quirks.
They're other preamps that eat tubes so to speak. Andr, Aesthetix didn't mention it being hard on tubes or requiring certain tubes.
The AI's in my personal experience are not tube eaters. That's all I can say and it is from personal experience. People jump on these bandwagons for whatever reason.
Andr, sorry, but what you tell is not experience in my book. You need to own one, live with it and then you can talk all you want. People have all kinds of reasons for selling and dealers have all kinds of reasons for dropping lines (usually something to do with profit margin.)
As for not putting NOS tubes in it, it is on the AI websight and a competent dealer would tell you. I would think they should have experience.
As for sound, that's up to each individual to make the call.
A lot of the preamps people bring up in comparison are not there to me. Try comparing side by side, not on memory of what you think something sounded like. It's the only way to know for sure. I've found a lot of other things bring about sound change.
Also, one last comment, Art and his crew have always been excellent with me. Art shipped my L2 to me so it arrived Christmas day! Try that with another manufacturer.
They are a small company and as such, are slower. However, patience is a virtue. They've been around long enough to see a bunch of other companies drop out and to me, they must be doing something right.