Siobhan Magnus won over three of the four judges on American Idol last night -- but it was Simon Cowell as usual who had the problem.

Cowell said he was "under impressed" after the Irish American singer belted out "The House of the Rising Sun" by the Animals and won heartfelt praise from the other three jurors.

Randy Jackson said that Magnus "came every week with a surprise. You take every risk, every chance."

Kara Dio Guardi stated the a cappela song was "brilliant." Ellen DeGeneres said, "You are why I love music. It's supposed to move you and it's supposed to do just what you did to me."

However, Cowell said part of the performance was "weird" to him.

Maguire was in a hot red dress and high heels, casting aside away the little-girl image she had from previous weeks. The crowd went wild as she danced and sang her way through the Animals' classic hitting all the high notes.

The star of the evening, however, was Crystal Bowersox -- who wowed all four of the judges singing Tracy Chapman's "Give Me One Reason."

"Right now you are the one everyone has to beat," Cowell stated. The top 12 finalists will be announced on Thursday night's show.