What component is responsible for dynamics ?

Watts are cheap, high powered SS amps with medium efficiency full range speakers can produce impressive dynamics.

High efficiency speakers will raise the noise floor, same with cheap tube equipment.

Without a very large enclosure, high efficiency speakers will lack low end due to Hoffman's Iron Law.

Bookshelf or limited LF speakers lack the necessary low end impact needed.

Having tried a few different speakers of different efficiencies in my rig over the last few days, I don't believe speaker efficiency has a direct correlation with perceived dynamics.

The two pairs of monitors I tried are a few dB more efficient than my reference towers and they appeared to lack in dynamics, I believe the lack of LF extension is directly responsible for this, although driver size could also be a factor. The towers are tuned to 20hz, meanwhile the monitors are tuned to 40hz and 55hz. The speakers contained a 10" woofer, 2 6.5" woofers, and a 5.25" woofer respectively.