Use 2" crown moulding

Hi cdawn, the size of the crown will depend on the height of the upper cabinetry, the ceiling height and any restrictions you may have adjacent to the cabinetry (such as taller doorways, shallow corners etc)

Generally speaking, the taller the cabinet, the larger the crown. A 36" upper looks proportional with crown in the 3-4" range. A 42" - 48" cabinet with crown in the 4-5" range and 54" and up 5-7" range or stacked. There are exceptions to every rule, so I suggest visiting a molding store and trying samples of various sizes and styles next to your cabinetry to see which you like best. If you search houzz for "cabinetry crown" you'll see many great examples of how the right size crown can make a big difference.

Steve