In general, Steelcase, Herman Miller, and Knoll are all pretty similar, and all considered top-of-the-line. Knoll is more design focused than the others, and also offers reproductions of pieces by mid-century designers, such as Charles Eames.
Steelcase makes a really great lower-priced line of office furniture called Turnstone: http://www.turnstonefurniture.com/. The line is geared toward emerging and cost-conscious companies.