These are all "Light classical" performers you have listed. It really goes in a classical sub-category called Pop classical, and there is no real slot for it in the Y/A categories.
You are better off re-asking this question in the Pop Music category, though. The classical folk do not care for it (very little to a very strong dislike, actually).
If you want some real classical music and classical singers, I've listed a few with youtube clips you can listen to.
Rachmaninoff: Vocalise, Anna Moffo, soprano
http://www.youtube.com/watch?v=kU8RwT8OD…
Schubert: Ave Maria, Elly Ameling, soprano
http://www.youtube.com/watch?v=W9sxwiNgn…
Schubert: "Der Hirt auf dem Felsen" Elly Ameling, for piano, clarinet and soprano - longish intro with piano and clarinet ---
(I/2 )
http://www.youtube.com/watch?v=rPpII4xTV…
(2/2)
http://www.youtube.com/watch?v=IIJKgRs2B…
Bach, Aria from the Wedding Cantata
http://www.youtube.com/watch?v=roabjXxxX…
Villa-Lobos Bachiana Brasieira No. 5, for soprano and seven 'cellos, one bass.
(1/2)
http://www.youtube.com/watch?v=M7vkmAkTv…
(2/2)
http://www.youtube.com/watch?v=Hf64-S8iJ…
Henry Purcell: Dido's Lament, "When I am laid in earth, Jessye Norman, soprano
http://www.youtube.com/watch?v=rvYgqg6_O…
Mozart: 'Dove Sono,' Jessye Norman, soprano, (start at 1'48'')
http://www.youtube.com/watch?v=VX27o382f…
Richard Strauss: Four last songs, iv, Im Abendrot, Jessye Norman, soprano
http://www.youtube.com/watch?v=0BzpoSJ42…
@ an Answer: Sorry, your Amici Forever clip is 100% verifiably not classical music.
best regards.