If you haven't already discovered a little gem of a garden center by the Goodwill Store in Lawrenceville, I suggest that you take a look.

Cavacini Landscaping and Garden Center - 100 50th St  15201 - is owned by a terrific young woman.  They have a nice selection, but not overwhelming, and from what I could tell, good pricing.  Perennials are $2 off, annuals are BOGO and they have friendly, personal customer service.