Thanks for the photo. To give this island bed a more tidy, professional look place the tallest plants in the middle using at least three of the same plant, each  shrub at least 5 feet tall. Perhaps 3 to 5 evergreens such as Ilex 'Sky Pencil' or Dwarf Alberta Spruce. Next use medium tall plants toward the edges at a lower height of perhaps 3 feet. Your cone flowers, sedum 'Autumn Joy' , tulips, daffs with low growing shrubs such as spiraea 'Magic carpet' or the tough shrub roses like the flower carpet rose. Again use repetition with at least five to seven of the same plant. Finally at the edges of the bed use low plants. For a formal look a border of dwarf boxwood or less formal the euonymus' Winter Creeper'. You can also use heuchera and heather repeating the same plant at least 5 times to give the bed a unified look. The edging plants should be under one foot tall and they don't have to be all the same, just groups of the same instead of dotting them about. If you like the ornamental grass, keep it as a focal point. If you don't like it use a birdbath, birdhouse on a post or some other non living garden accent as your focal point near the middle of the island garden. It will be lovely, trust you instincts. Keep growing, Marianne Binetti