It depends. Music wise only, it has to be High def stuff, which I am only slowly acquiring on priority basis when I have time....as far as the large sound system is concerned. Its quality only really makes a difference when its bluray movies etc.
For the headphones, yes I can find a difference even holding everything else constant quality wise....because of the direct insulated contact....which I find makes the differences more perceptible. This works both ways however, if the recording is even a little bit on the bad side, it will stick out like a sore thumb as opposed to getting smoothed out.
But when the recording quality is good to excellent, it is on a whole new level for end hearing quality.
I have older sets of headphones handy so I can always check the difference to appreciate it.....I use these older sets when I have only 1 version of some music and its mediocre to poor quality. A lot of my Maria Callas rare stuff and also some Indian carnatic music (which I converted from tape to CD/electronic) for example fits in this category....and till I find high quality stuff (which probably never will happen given the rarity), I have little other option.