Use a frequency analyzer plugin (or stand-alone editor like cooledit) to zero in on the vocal range.You can then program the parametric EQ to create the space you desire.
This is really a rather awkward and inelegant solution,however.Mike placement at the initial tracking is the real key in making an instrument "sit down" in the mix.As the arranger,you must plan how to use your sonic space.Always ,its the mids that clog things up.Vocal,guitar,keys,etc.Gotta slice and dice those frequencies during tracking via mike placement or EQ to avoid gouging great scoops of frequency from a poor instrument you have sacrificed on the altar of poor planning.
Tom