Any point in adding tube preamp to SS integrated?

A tube DAC or tube phono pre would get you that tube "magic".

I like 4tc's. The only reason I see to get rid of them is to change personality, ie nordost flatline is no better but may have better high freq. resolution???

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).

I would be very hesitant adding the gain that a preamp might add. If you can find the input max voltage and the voltage out of the tube pre I bet it will be far in excess of the capacity if you have an amp out or a pre in option which some older integrateds do (e.g. most Sansuis c.1980). It's clearly easy to do but unlikely in the Classe.
Beside that a tube buffer is a buffer . I understand that it's main function is to give the signal source a friendly impedance not a autoformer but a lower impedance than for example the typical input inpedance a CD player meets going into the preamp. There is no tube halography doing this but your CD player will sound as good as it can depending on the what the power suplly to the buffer allows.

Now
If you have heard tubes at their best you know they are incomparable IMHO and further you know what it is you like about it.
The only way! I am convinced is to fish or cut bait- and do it - use tubes all the way.That is if you really want to hear what the tube aficionado finds so appealing then start where most err by avoiding the use a tube power amp first.
Yes it is the most critrical element in obtaining tube magic. Honest the old theory that a tube somewhere in the chain will make the system sound like a tube system is completely,and utterly false.I generally say IMHO but after years of doing everything but using a tube power amp. I finally found nirvana doing just that.
Trelja a member here and old friend told me he had known this for a long time. I was floored because he saw me waste all this time and money trying to get it.
You'll save time and stop wondering what all this tube mania is about. Try it or just borrow a tube power amp you will see.
BTW I tried all tube preamps with SS power amps and that helped but didn't really yield the tube's importance to the sonic. From day one (of this hi end business)I had a tube CD player nope not that either.One caveat if you get lousy tube amp you only get the magic "forme fruste".
I found that both tube preamp and separate tube monoblocks worked out best. I have had Nirvana with scarcely a change in over 3 years.
Good luck on your journey and don't blow the Classe or your speakers to bits