What component is responsible for dynamics ?

Comparing a small monitor to larger box floor standing speakers misses the point entirely.
Charls

So as is typical on such posts, the answer is everything and nothing.

Tbg,

That's because the answer is all of it. Each part in the chain
contributes to the sound. Or in this case the dynamics.

It is a silly question that's why so many silly answers/non answers.

Chad,
Actually many posts do agree that all components matter. If someone was putting together a new system, high efficiency speakers would just be a very good and logical place to start, that`s all. This would avoid the mandatory need for a huge mega watt amplifier as a prerequisite to obtain dynamics.
Best Regards,

Charles1dad, It would appear to me that high efficiency speakers are often more huge in comparison to low efficiency speakers, than mega watt amplifiers are huge in comparison to low watt amplifiers.
It appears as though, very often high efficiency speakers cost more and offer less extended frequency response than comparably priced low efficiency speakers. Furthermore, it appears to me that many systems that use high efficiency speakers use amplifiers that have lower watt output, but those amplifiers often actually cost more at purchase and there after. All in all, IMHO, high efficiency speaker systems appear to offer less value. As such, I disagree with your assertion that "...high efficiency speakers would be a very good and logical place to start,...).