Privacy Hedge

I planted a row of "Rose of Sharons" as a privacy hedge last year. I didn't realize they were such late bloomers. They are just beginning to bud while everything else here in New England has been green for a month already. Anyway, I'm thinking of interchanging a few of the Rose of Sharons with another shrub such as Viburnums or Lilacs so at least I'll have some color while waiting for the Rose of Sharons to fill in. I'm worried how this will look several years from now. Should I just leave everything as is? I need as much height as possible but I can't have too wide of a spread. Anyone have any suggestions?
Thanks, Till
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