Duh, speaker, of course. Everything in the chain matters. But speakers vary significantly more than any other link in the chain(the cartridge is second in an analog system) so their choice gives many more variations to find sound you like and conversely it is by far the link in the chain that can produce sound you don't like and there are probably many more speakers whose voice you don't like than you do like.
Poll: Most impactful component
Given all the technological advances over the years, audiophiles have very different perspectives on equipment.
This likely reopens an age old debate, but which component has the most potential to improve a stereo system? Or can it?
If you could upgrade one component to take your system to the next level which one would get the investment? Speakers? DAC? Pre? Source?
Or is this the holy grail that no one can achieve?