The Pampas grass I believe you are referring to is the one that produces the the large fluffy white plumes commonly seen in southern landscapes, and it is not hardy in our zone 6. In Kentucky Erianthus ravenne (Plume Grass) is called hardy pampas grass is used as a substitute. Grasses are not evergreen and are cut to the ground every spring when the tops are killed back by the winter weather.
A tall shrub border can include one or several different flowering shrubs like Forsythia, Mock orange, Viburnums and Weigela.
For more information contact your Cooperative Extension Service in Oldham County KY.