By all standards, this was a big show. The crowd was big. The stage was big. The visuals were spectacular. Even the opening act brought an extra dose of star power.

Rascal Flatts is one of the biggest acts in country music, and like other big acts in country music (Kenny Chesney, Taylor Swift), its popularity has a lot do with its mainstream sound, which bears little resemblance to country music.

Saturday night, Rascal Flatts opened the 2009 leg of its Bob That Head Tour at Sprint Center. It was the trio’s second show at Sprint Center in about 15 months, and like that show, this one was a near sell-out. (It looked like there were fewer than 1,000 empty seats.)

That big crowd was treated to a high-energy spectacle. The stage included runways and stairs that extended into the seats on the floor. All night the two-story video towers behind the band displayed all kinds of light and visual effects, including an impressive animation skit near the end of the show. During the encore, a blizzard of confetti and balloons rained on fans in the lower sections and on the floor, which incldued a general-admission section at the back.

The show lasted nearly two hours and the setlist was loaded with hits and familiar tracks pulled from a discography that goes back to 2000. Their fans — men, women, boys, girls, young adults, elderly couples — sang-along and swayed to those songs all night.

The boys — Gary LeVox, Jay DeMarcus and Joe Don Rooney — rely on a familiar, predictable formula, but it’s a formula that remains fail-proof and keeps them on top of the country radio charts. It has also made them one of the most successful touring acts of the past few years. They also live by country music’s first commandment: Respect your audience. So they expressed plenty of down-home love to their fans.

The Flatts’ music is non-denominational pop — songs with roots in rock, pop and even a little pop-R&B. On “Bless The Broken Road,” they sounded like a mix of the Backstreet Boys and Boyz II Men. Most of those songs are sculpted and polished for a mainstream, crossover crowd that prefers sugar to spice. Some of those songs are smart and well-crafted; some are cliched and overly sentimental.

Either way, their fans eat it all up. So the mood in the arena was bright and upbeat all night, from the explosive opener, “Still Feels Good,” to the raucous closer, “Bob That Head.”

This spring, the Flatts will release an album they’re calling “Unstoppable.” Expect it to do well in stores and on the radio charts. And don’t be surprised if they come back to town before the year’s over and nearly fill an arena or amphitheater near you. They are that big.

Jessica Simpson: She opened the show with a set that included “Remember That,” the single off the country album she released last year. She has a big voice that carried itself across the arena, but her 40-minute set was pleasant at best. An act like hers seems better suited for smaller rooms