Any point in adding tube preamp to SS integrated?

IMHO, you won't hear much 'tube magic', whatever that is, by adding a tube pre-amp ahead of the CAP101. What it will do, and it may be a good thing, is allow you to assert some influence on the tonal balance by using different tubes in the pre-amp and tune it to your sonic preference. I assume (but do not know) that the CAP's line stage is passive. If that is so the pre-amp might add a bit of drive/energy to the sound as well. You can use the tape in, or for that matter, any of its inputs (other than a phono phono input if it has one).

IMHO, Re the probability of the addition of a pre-amp adding extra gain and creating a gain overload, consider that the VC on the CAP would attenuate the gain from the tube pre-amp just as it would any other source - the worst thing that would likely happen would be you would lose a lot of the flexibility of the VC on the CAP.

A potential mismatch could occur if the tube pre-amp has a high output impedence as many do, but considering what you are doing it might well be benign. I wouldn't let the gain issue stop me for a moment.

However, as I indicated earlier, I don't think you will get real 'tube magic' anymore with this addition than you did with your buffer (a conclusion you may already have reached). But you bend the tone provided that the pre-amp you use benefits from using tubes which have greatly varying sound (like 12AX7's) and are cheap. I mention this only because I find a lot of folks think 'tube magic' has something to do with mid-range or lower mid-range warmth, high frequency 'sparkle' and a lot of other tonal issues, as opposed to spatial, liquidity, and proper decay issues which is where I think tubes can excel and SS often falls short.

FWIW.