Which has a greater influence on sound quality, the amp or the preamp?

Both can, and do affect sound quality. Every component and interconnection in the chain affects the quality. Depending on your source you don't always need a preamp in the system. 

You may not need active preamp in the system but you will always want it, whether you know it or not.

@inna Not me, I'm very happy with my Tortuga Audio LDR Passive Preamp.

It lets me hear what`s in the recording without adding any unneeded flavoring.

Crystal clear sounding, never needs warming up either. Very easy to hear changes like rolling tubes or cables etc etc.

Also, with the numeric volume display showing 40 ( it goes up to 70), my system is playing about 85 db (too loud imo)

More people should try one and see for themselves 👍

@scm 

I’m with you. I’ve had preamps from Pass and Herron. Very good stuff.

But, I’ll stick with my EM/IA Remote Autoformer (pure silver) all day, every day. When I put that sucker in my system it was one of those glorious audiophile days. In the year or two since, I have not thought about wanting/needing anything else.

Though I’ve been told I may not know it 😆

Well, sound preferences differ, so do preamps. As far as I know, most audiophiles do have active preamp in their systems. Going direct can give more pure but less refined presentation.