When four UFC champions and their next opponents stood together on a stage Tuesday amid camera flashes and raucous cheers, the happiest man was in the middle.UFC President Dana White has healthy fighters, pleased television partners and a tantalizing slate of upcoming fall fights. It's a big change from last year, when White spent untold months scrambling to replace injured stars and plugging holes in an ambitious schedule that devolved into a patchwork slate for mixed martial arts' dominant promotion."It feels good to run your business again," White said. "You're on your heels the whole year, rebuilding cards that were already built and not focusing on building your business. Right now, everything couldn't be better."The unprecedented cancellation of UFC 151 last September was the lowest point in a year crammed with injury postponements and underwhelming cards. Many fans thought the UFC had booked too many shows with not enough quality fights to fill the schedule demands of its television deal with Fox."Last year, we had main events and co-main events falling off every card," White said. "This year doesn't compare to last year. We're really building some momentum, and these fighters are going to keep it going."White largely blames last year's problems on injuries, and most of his important fighters are healthy heading into the fall. Every star fighter on stage for the promotional event at a downtown Los Angeles theater is eager for a starring role this fall.Georges St. Pierre, Ronda Rousey, Jon Jones and Cain Velasquez displayed their title belts and signed autographs for hundreds of fans on the Hollywood stop of an unusual six-day, 11-city promotional tour stretching across three continents. The champions traded barbs and posed for faceoffs with challengers Johny Hendricks, Miesha Tate, Alexander Gustafsson and Junior Dos Santos.St. Pierre, Rousey and Velasquez drew the biggest cheers from the crowd, which reserved its biggest boos for Jones and Tate. Jones, whose refusal to accept a late replacement opponent at UFC 151 partly forced the card's cancellation, has become an antihero to UFC fans despite his sparkling record and boundless talent."You guys like to boo me, I'm realizing," Jones said with a grin to the jeering fans. "I feel like I'm growing up in front of an audience. But it's fun. It's a great business to work in."Jones and Gustafsson will meet for the light heavyweight title in Toronto on Sept. 21. Hendricks gets his long-anticipated shot at welterweight champion St. Pierre in Las Vegas on Nov. 16, while Velasquez and Dos Santos will complete their trilogy of title fights in Houston on Oct. 19.Rousey, the UFC's breakout star of the last year since the promotion opened a women's division, defends her bantamweight title against Tate on Dec. 28 in Las Vegas. Rousey and Tate were the only fighters betraying a serious dislike at the promotional stop, exchanging insults to the fans' delight."How is it not a rivalry? I have everything that she wants in life," said Rousey, who repeatedly made obscene gestures at the challenger."She just has a way of irritating me," Tate replied. "It's really more of a personal thing."The world tour features most of the UFC's biggest names, but it doesn't include Anderson Silva, whose streak of 10 straight middleweight title defenses ended earlier this month with his shocking stoppage loss to Chris Weidman. Their rematch will headline the UFC's traditional year-end Las Vegas show on a card also featuring Rousey and Tate, but Silva had sponsorship commitments that prevented him and Weidman from joining the tour.Silva's defeat served as a sobering warning to St. Pierre and Jones, two long-reigning champions who have often seemed as untouchable as Silva. St. Pierre will risk his streak of eight consecutive title defenses against Hendricks, the bearded wrestler who has waited years for his opportunity."I would never take anything for granted or look past any opponent," St. Pierre said, still smarting from his stunning upset loss to Matt Serra in 2007. "I made a mistake before, and I paid for it, and I'll never do that again."Hendricks and Gustafsson are eager for their long-awaited title shots, and Hendricks believes he's ready to end the Canadian welterweight star's reign."I'm stronger than anybody he has ever faced," Hendricks said. "I hit harder than anybody he has ever faced. I'm quicker than anybody he has ever faced."