As if winning a Grammy wasn't enough to keep Lady Antebellum riding high, the group has more reason to celebrate. The trio's sophomore album, 'Need You Now,' has debuted in the No. 1 position on Billboard's multi-genre Top 200 chart, with first-week sales of more than 480,000 units. It's the biggest debut sales week for any album since Susan Boyle's 'I Dreamed a Dream' moved 701,000 units in its first week in November 2009, and the best first-week sales for a country disc since Taylor Swift's 'Fearless' in 2008.

"We are absolutely stunned. The love and support we were feeling last week from the fans and everyone around us was so incredible," says Lady A's Dave Haywood. "These songs are about our lives; they're really personal. And to be getting such awesome feedback from everyone who bought the record is so validating."

On Sunday night, the trio took home a Grammy for Best Country Performance by a Duo or Group for the No. 1 hit 'I Run To You.' Following their performance of the new album's title track -- and multiple-week No. 1 smash -- 'Need You Now' on the awards show, the song topped the iTunes digital singles chart encompassing all musical genres.

"We were so focused on making that Grammy performance the best it could possibly be," says Hillary Scott. "We put all of our emotions into it, and really just went for it. We'll never forget what an amazing week we had!"