I'm a big new age music fan and often compose music in that particular style. I think that larger dedicated choir libraries may even be an overkill for the new age genre, so my choice would be something that is more reminiscent to the choir and voice sounds found on traditional keyboard workstations and modules, especially those from Roland and Korg. Not a realistic choir per se, but something that is choir-like.
As a Kontakt and Komplete user, my personal favorites and obvious choices would be Phoenix from FrozenPlain, all the libraries from Sound Aesthetic Sampling, Iron Pack Bundle and Holy Ambiances from Soundiron and last, but certainly not the least, the choir sounds found in Kontakt Factory Library which are IMHO very adequate for new age music. In addition to those, I also have Olympus Elements choir and Clara's Vocal Library (the free version), but as I've wrote before, those may even be bit out of scope for more traditional new age sound.