A pair of high-profile HBO pilots -- "The Wire" creator David Simon's New Orleans drama "Treme" and the Martin Scorsese-helmed "Boardwalk Empire" -- have added to their casts. Steve Zahn is in talks to play one of the lead roles in "Treme," which looks at post-Katrina New Orleans through the eyes of the city's community of musicians. Kim Dickens ("Deadwood") has also signed on to the cast, which already includes Khandi Alexander ( "CSI: Miami") and "Wire" alumni Wendell Pierce (a New Orleans native) and Clarke Peters. "Boardwalk Empire," meanwhile, has added British actor Stephen Graham to its ensemble, according to The Hollywood Reporter. "Treme" would be Zahn's first regular role in a TV series. The "Out of Sight" and "Perfect Getaway" star would play a DJ and musician who's a proud native of the Crescent City. Dickens, who's currently on NBC's " Friday Night Lights," will play a chef who has an on-and-off with Zahn's character. "Boardwalk Empire" is about the rise of Atlantic City in the early 20th century and centers on a liquor distributor played by Steve Buscemi. Graham will play a young Al Capone, who's working as muscle for a Chicago gangster and strikes up a friendship with one of Buscemi's lieutenants (Michael Pitt). Graham, who co-starred in "Gangs of New York," plays another famous criminal, Baby Face Nelson, in Michael Mann's summer movie "Public Enemies."