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.
