With extravagance so palpable in the movie “Bernard and Doris,” the opening night hit of the 2007 Hamptons International Film Festival, soon to air on HBO, you'll think the budget was unlimited. But no, said director Bob Balaban at an extravagant celebration for the film at the Time Warner Center last night: “You will see Susan Sarandon in a red ball gown about 9 minutes in. I said to a guy I met on the subway upon hearing he was a designer, can you make a dress? I'll give you no money, not even for the fabric.” Sure enough, about 9 minutes in, Sarandon, sublime as billionairess Doris Duke, swans down a staircase in red satin. Such is movie magic. Of course we know Balaban, the kid actor in the 1969 “Midnight Cowboy” to the Christopher Guest movies and more. But several years ago he directed a gem, “The Last Good Time” about a tender relationship between an elderly man and a teenaged girl, and with the late director Robert Altman he co-produced "Gosford Park," which like an old fashioned British mystery, featured the rigid class divisions of upstairs and down. Now in this new film he's at it again: what happens when that line is crossed? Bernard Lafferty, played by Ralph Fiennes, is a servant who becomes so much more to Duke, he eventually inherits her fortune. But this is no “Lady Chatterley's Lover!” His orientation is such that the two become drinking buddies playing dress up among the orchids in the green house. Balaban is especially adept at showing the stages of the evolving relationship between these eccentrics. Duke, it turns out, was particularly and arbitrarily cheap, firing servants for swiping booze (understandable) and for wastefully disposing of a wedge of cold cantaloupe (not). And Fiennes! So brutal in “In Bruges,” his other new film shown at Sundance last week! Here is another side of this actor, sexy even when applying mascara. A crowd worthy of “Who's Who” spilled into Porterhouse for supper: Harry Belafonte kiss kissed with Sandra Bernhard, writers Calvin Trillin, Jay McInerney, Nora Ephron, Dominick Dunne, Gay Talese schmoozed with uber-agents and editors Lynn Nesbit and Nan Talese. Wallace Shawn sat with Fran Liebowitz. Sidney Lumet, closed out of the awards for his superb “Before the Devil Knows You're Dead,” will nevertheless enjoy a retrospective of his work at Film Forum. Aida Turturro chatted with Ellen Barkin-one could not miss the irony here-who chatted with Susan Sarandon holding court in a cleavage-baring red dress. Someone asked, What's Rush Limbaugh doing here? Oh, he came with Cindy Adams, said Sarandon. Cindy bought Doris Duke's apartment and felt so proprietary she gave the film a wrap party. Not to worry. Limbaugh was balanced by the presence of Air America's Randi Rhodes