Karmazin Brings Sirius Starpower to Radio (washingtonpost.com) washingtonpost.com - Sirius Satellite Radio's hiring of former Viacom President Mel Karmazin as its new chief executive is its most aggressive move yet to steal market share away from larger rival XM Satellite Radio. It's also the clearest signal so far that the satellite upstarts intend to be real competitors in the media world.