Most important component??

Let me consult my crystal ball. Close your eyes and concentrate...

Instead of individual components, I see component pairings.

The loudspeaker-room pairing looks like the most important, as this is where there is the greatest variation.

Next, depending on what speakers you decide work well in your room, the loudspeaker-amplifier combo may well be the next most important pairing. In some cases, it's appropriate to consider the speaker wire as part of this combination, but not always.

If the loudspeaker isn't all that particular about what amplification is driving it, then the preamp-amp pairing is probably the second most important.

After that, my crystal ball gets too cloudy for me to see clearly what comes next.

Slip me another twenty dollar bill and it will probably come back into focus...

Duke
dealer/manufacturer

most important component? I would say your "EARS".

The room, without a good room or plenty of proper treatments and placement nothing else really matters because it will never be allowed to shine, I lived in bad rooms up till a few months ago.....it is a huge deal.

Chad is 100% correct. I inherited my daughter's room when she went to college last fall. The room had bare walls when I put my system in place; sound was terrible. After experimenting with room treatment in different locations the sound has improved immensly. The speakers remained in the original location but the changes in the room affected the sound for the better.
As for components you mentioned, speakers make the biggest difference and I know because I rotate three different pairs in and out.