If you are asking for advice about which one for you???? It depends on what you are trying to achieve.
This is all general and a given piece can make it all wrong...
So, In general, If you are after that So called Tube Bloom and you have pieces that all 3 give that bloom, the amp will add the highest degree of bloom. Depending on the cartridge and phono section, it could be either after that, Although, for me, I would rather not have a overly rich phono cartridge with a phono section with a lot bloom... So it could be the Pre or phono section either... Of course, if you are trying to add that Richness or Bloom as I've been calling it, if you grab it from your amp or pre, you can then have it throughout your system, rather than your phono section only....
But, if you truly just like a certain Tubed piece because it is just better than the ss counterparts that you've tried, I would then recommend that you just get the tubed component that you want.
I hope this makes sense,
Tim