What component is responsible for dynamics ?

all of them (IMO) but,

a reasonable approach would be to get some high efficiency full range speakers and the proper power amp.

but the answers are going to be all over the place.

Hmm.. To simplify, perhaps grossly, and to generalize, I would say power amp and turntable itself, not arm or cartridge, or cd transport. Stable current from the wall is very important too, of course.

Everything in the system, from the quality of your AC, to the size/layout of your acoustic space, can and will affect the dynamics of what you hear.

I remember reading a post many years ago on Audio Asylum where a recording engineer measured the compression of dynamic peaks in various loudspeakers, and found a strong correlation between loudspeaker efficency and preservation of dynamics. Unfortunately that post has apparently been removed so I can't post a link to it.

Duke
dealer/manufacturer

The system as a whole and it's synergy with each component and connection are responsible for how dynamic your system is.