LEONA LEWIS Simon Cowell has been nattering on about singers having that certain special "X factor" for several years on "American Idol." He liked the idea so much that he turned it into a reality contest in his native United Kingdom, and Lewis was the 2006 champ. With her curly locks, biracial ethnicity, and skyscraping range, Lewis has drawn comparisons to Mariah Carey (and Whitney Houston and Celine Dion). The 21-year-old also drew copious praise from judges Cowell and Sharon Osbourne, celeb blogger Perez Hilton, and other British pop stars such as Gary Barlow of Take That. In November, her "Spirit" became the fastest-selling debut album in UK history; it arrives on these shores in March.