My opinion the source has made the biggest improvement in my experience. To me the source provides the overall sound quality, soundstage, dynamics micro/macro, separation of vocals and instruments, placement, dimension and most important to me is the tone of the instruments. Other components contribute to this sure. For example, I love to hear a piano and the decay of the notes. To me the right source provides this which allows one to hear the "wood" of the piano and the size of the strings the hammer is touching. Some components are just too fast and to me that sounds like a kind of cheap toy piano. Very hard to explain until you hear it. If that is not correct to my ears, then to me nothing in the system can compensate for that. Also micro to macro back to micro dynamics, without that you don't really hear the emotion in the voice or string instruments. And then there is a black background. At the last CAF one reviewer said in his review of a digital product that it was eerie quiet. So instruments come out of space and dimension.
Well that is all I have to say on this subject. Happy Listening to all!