Several sources confirm that CBS is in negotiations to extend TV’s top-rated comedy Two and A Half Men into a ninth season. The sitcom that stars Charlie Sheen and Jon Cryer shows no sign of slowing: Its sixth season premiere on Sept. 22 was up 9 percent in viewers (14.9 million) and posted its best performance among young adults since 2004. Once the show’s contract extension is finalized, CBS will get busy re-signing the already well-compensated actors (Sheen, for example, gets a reported $825,000 an episode), all of whom have deals that expire next year.