@calvinj , I am also going to say that in my small untreated flawed room with the speakers and front end that I now have on board, what I now hear that makes the biggest difference in SQ is due to the quality of the source material. I am (for good or for ill) all digital, and I am not just referring to my taste in music. I am not a huge jazz fan, but over the past couple of years I have been trying, and although it is not my favorite genre, some of the jazz SACDs I have bought over the last few years have some of the best sonic quality ("more musical", ha ha) in my collection. And then there are CDs in my collection from genres that I really like and those from genres that I used to really like that have the nails-on-a-chalk-board-effect on me. I have SACDs that are nothing special in SQ as well . . . on the other hand I have red-book stuff that I am totally blown away by, and I assume it is my front end (most specifically the SACDP) interacting with a "well" recorded mixed and mastered disc.
Which leads me to conclude that the very front of the system MIGHT be the most important link in the entire chain. But since I know that is an invitation to pushback, I am going to qualify that by saying that I am only speculating as a mostly satisfied and not disgruntled consumer who loves the sound of his system in a small bad room when it (the system) is getting things right.