Where exactly is Sugarland? Hard to pinpoint. When Jennifer Nettles and Kristian Bush are rollicking through "Down in Mississippi (Up to No Good)," they're deep in the heart of honky-tonk. But country's latest dynamic duo—since founding third member Kristen Hall left in January—can two-step right over genre lines. That was Nettles dueting with rockers Bon Jovi on their "Who Says You Can't Go Home" and hobnobbing with Sir Paul McCartney at the Grammys last February. "It was surreal," Bush recalls. "It's still shocking that there's a Beatle who knows who we are." On tour, where they're opening for Brooks & Dunn all fall, the two veterans of Atlanta's singer-songwriter scene keep life on the road more hippie than homespun: leather journals, patchouli-scented candles, a humidifier (for her), hypnosis tapes (for him), yoga (for both), plus a high-tech touch: two very busy BlackBerrys. "Always the BlackBerrys," says Nettles, 32, who uses hers to e-mail her husband while Bush, 36, uses his to stay in touch with his wife, son, 4, and daughter, 1. While touring, "we're a self-contained unit, like a submarine," Nettles says, but Sugarland's significant others back home don't worry about a tour-bus romance. "They're more jealous of the road than they are of either one of us."