Give these two a shot. I think you will like them and you can listen to samples before you buy.
http://www.amazon.com/Keeps-Gettin-Better-Decade-Hits/dp/B0031SBOKI/ref=sr_1_2?s=music&ie=UTF8&qid=1352007371&sr=1-2&keywords=christina+aguilera
http://www.amazon.com/Christina-Aguilera/dp/B00000JY9M/ref=sr_1_4?s=music&ie=UTF8&qid=1352007371&sr=1-4&keywords=christina+aguilera
http://www.amazon.com/Keeps-Gettin-Better-Decade-Hits/dp/B0031SBOKI/ref=sr_1_2?s=music&ie=UTF8&qid=1352007371&sr=1-2&keywords=christina+aguilera
http://www.amazon.com/Christina-Aguilera/dp/B00000JY9M/ref=sr_1_4?s=music&ie=UTF8&qid=1352007371&sr=1-4&keywords=christina+aguilera