David Brown is stepping down as host of American Public Media'a Marketplace, the daily business and finance show produced here in L.A. Brown says, "I am very excited about starting a family with the girl of my dreams, working on my journalism doctorate and digging deep into the Texas music scene." In 2003 he replaced David Brancaccio, and so many listeners thought the two sounded alike that Brown ran a feature comparing their voices. The new host is Kai Ryssdal, the host of "Sound Money" and "Morning Report." Romenesko has the memo from executive producer J.J. Yore.