Importance of Amplifier versus Preamp?

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?

If you are seeking optimum performance it is not wise to over or under emphasize any component.