With Reagan-era nostalgia on the rise, Daryl Hall & John Oates picked a good time for a comeback. But they're not the same men they were during the early days of MTV. More acoustic soul than the Motown hand-me-downs they pumped out in the '80s, Do It for Love is the sound of weathered romantics chastened by years of business and personal turmoil. At times, the smooth-groove appeal remains: ''Man on a Mission'' and a version of the New Radicals' ''Someday We'll Know'' have the ardent falsetto harmonizing and hooks of old. But after a strong start, the CD settles into a lite-FM haze of drowsy songs and light-as-meringue arrangements.