My collectinon was originally built around a desire to own a fairly complete collection of the important pre-quartz auomatic movements.That means I own a number of watches that fall well below the average quality I own. However, they are not mere "quantity" watches; they are still required for completeness.
I also own some watches that I enjoy but are not necessary to the completeness of my core collection. I would sacrifice those for a "grail" watch if I had one. However, for me it seems the grail is the core group of watches rather than any individual watch.