Importance of Amplifier versus Preamp?

It's an easy experiment.
First try running without an amp.

Then try without a preamp

Which is more important will become perfectly clear.

Overall, as far as this thread goes; I'm in agreement with Mapman. If I needed RIAA eqing, perhaps I might feel differently.

I'll agree pre-amp is probably the most important tweak and if you are running a phono you need one.You also need a volume controll. ANd maybe a way to switch multiple input sources if you have those. A pre-amp is just one such device to serve those functions when needed. Other than that, its just a potentially expensive signal processor that is not very flexible compared to the alternatives.

These days, it pays to consider function, not form. A traditional preamp provides various functions that may be had equally well or better in other forms these days.

The preamp is the air-traffic cotroller. The amps are a plane.

I think its a toss-up. Isn't it true that a really good amp will make just OK speakers sound their best... but really good speakers will never sound their best with an amp that's not up to the task?