"Send the box of chocolate to me!"
Translation:Sendu la skatolon de ĉokolado al mi!
Yes, "de" describes a quality, while "da" describes a quantity. "Salono de ŝtono" is indeed a hall made of stone, while "salono da ŝtono" would be "a hall-ful of stone".
For this particular sentence, it seems to me that "skatolo de ĉokolado" is more appropriate, since what's being sent is a box that happens to contain chocolate. "Skatolo da ĉokolado" would be analogous to "kilogramo da ĉokolado", that is a certain quantity of chocolate is being sent, without describing how it is packaged.
Hope that makes sense :)