What is most important part of a system?

Do not expect any consensus among the answers which will be provided, or among the answers that have been provided about similar questions that were asked in the past.

Some will say the source is most important, because its shortcomings cannot be compensated for by any of the downstream components. I dispute that rationale, for two reasons:

1)That logic ignores the DEGREE to which different types of components may have shortcomings.

2)The source can't compensate for the shortcomings of the downstream components either.

Some will say the speakers, because in general they (and their interaction with the room) arguably make the biggest difference in the character of the sound that is heard.

Others will say the preamp, contending that it is "the heart of the system."

My own answer, expressed in general terms, is that a chain is as strong as its weakest link, wherever that link may happen to be located in a particular system.

And more specifically my own perspective leans in the direction of "speakers first," but to a greater or lesser degree depending on how "important" is defined (especially the degree to which price is reflected in that definition), and depending on whether the source is analog or digital, and depending on the degree to which the particular listener values deep bass extension and the ability of the system to handle recordings having particularly wide dynamic range.