Help me figure out this teen sci-fi/magic book, deals partly w/ the holocaust.?

[moonprincess7070]

I remember a book I read in about 2006 or before. It was the last book in a series about teenagers with super powers. I'll try to describe the book as best as I can. There are like 4 teenagers all with different superpowers that somehow saved the world in the earlier books. Somehow they end up helping this millionaire revive the people who died in the holocaust by mixing all the ashes in a room with the kids and them using their powers to bring them back to life. At one point they end up in a different dimension where the body of one of the teenagers is still at (though she's dead) in the end the kids have saved many holocaust victims and they all live in this city run by the millionaire.

That's all I can remember! PLEASE HELP ME! <3 I promise full points to whoever can get me the name!