ACTS FORGE AHEAD WITH NEW VOCALISTS AND ENJOY NEW SUCCESSES October 08, 2009 — 12:00 am PDT Nick Krewen / GRAMMY.com At the apex of Styx‘s popularity in the 1970s and 1980s, many of the Chicago rockers’ Top 10 hits came from a single songwriting source. Not only did cofounder Dennis DeYoung pen such Styx hits as “Lady,” “Babe,” “Come Sail Away,” and “Mr. Roboto,” but his signature vocals played…