Poll: Most impactful component

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.

Right now my source is the weakest component. But my room is not great either.

Source is usually easier to fix, so work on both... 😎

Cables and risers….. 😂Friday night laugh 

Cheers

1- The source material, of course.

2- The speakers and room (the two are inseparable).

To be meanful, I think you should reframe your question to what component(s) you have changed so far make(s) most impactful improvement, instead of what would you predict it to be. In my case, the first time I felt the system had an dramatic improvement is after changing the amplifier to Parasound A23 and NC 2125 v2. The bass is weightier and more nimble. The second experience I had is after changing my source from laptop/Mac to a streamer (ifi ZS), the top is more open, more airy, all range of sound has more clarity, background is quieter, etc.  The third improvement is resulted from a $5 gadget, i.e., drum stopper gel silicon. I double stack them and place on each corner of bookshelfs.  The bass is more solid and a bit more "bouncy".