Tube Preamp with Solid State Amp?

The short answer to your question is YES...depending on the pre-amp.  I had a parasound a23+ and p6 pre and picked up a Linear Tube Audio MicroZOTL preamp and put it in my system and it was an eye opening experience.  Never knew my music could sound so good.  I then replaced my amp with a pass labs amp and again it was revelatory.  The catch is the preamp alone cost significantly more than the parasound amp and preamp together...so you do get what you pay for.

Pardon the potential silly question, as I’m new to the idea of separates. I’m thinking of a solid state amp with a tube pre-amp. Do some / many / most tube pre-amps have the ability to bypass the tubes and go solid state when desired? This seems like it would be the best of both worlds, no?

Nope

Short answer, no, hardly any of them.  There are some DACs with both tubed and SS output stages but I cannot think of a single preamp, although I suspect there is one somewhere.  Of the several tubed preamps I have owned, and even the hybrid Lamm amplifiers I have owned, none of them provided what I would consider a tubed sound as you would get with most tubed amplifiers.  As I indicated to the OP earlier in the thread, IME, if you want a tube-type sound, get a tubed amplifier. 

While I have long been a fan of heavy Class A amps that never seem to run out of steam, I have actually gone all tube in my main system and really like it.

I also had tube pre and SS power for a bit. Either can work but it is system dependent and the only way to tell if you prefer it is to give it a try.  You can always sell whichever you like less.