For only $39.99 (normally $430), get Aurora Choir by ARIA SOUNDS!
The Aurora Choir is an elegant and powerful choir sample library for Kontakt (full version 4 or higher required).
Weighing in at 11GB, this massive vocal library contains both Sopranos and Altos (separate instruments for maximum control), and has an absolutely stunning legato tone. On top of this, it has short syllables, arranged into a very conveniently playable sequencer. Simply arrange your phrase in the sequence, and play away – the choir will automatically sing the syllables you enter.
The choir contains four true legato modes (ah, eh, ih and oh) sampled at multiple dynamic layers, giving a total of EIGHT true sampled legato sets, for absolute realism and variation.