You asked this same question 7 months ago.
http://www.korgforums.com/forum/phpBB2/ ... ht=#334730
The answers given by Axxim and X-Trade still stand.
Start with DWGS waves VoxPad1, VoxPad2, VoxPad3 for choirs. Other good ones are FlutePad, SynVox1, and SynVox2. Then modify EG1 with ADSR values for a pad, slow attack, long release. Then add FX, ensemble, stereo chorus, reverb (Hall-Long), in that order.
Go ahead, buy an M1. It's not likely to help. This is a simple program, and most of the work is already done for you with the DWGS wave. Plus the R3 can do far more advanced choirs using the vocoder to record formant motion, allowing you to record whatever vowels or words for the choir to sing.