I second the Fairfield Four, but would suggest that "Couldn't Hear Nobody Pray" is more 'accessible' (Standing in the Safety Zone is classic but it sounds as if it is mostly recorded off old 45s and while it's great gospel, the recording quality of CHNP is MUCH better).
I am also a big fan of Arvo Part choral music (my personal favorites are "Orient & Occident", "Miserere", "Magnificat", and "De Profundis", and some of the more recent recordings of the Berliner Messe). I find his music to be both beautiful AND intellectually stimulating though one has to be able to accept listening to unabashedly religious themes (a good deal is in Latin but there is no mistaking what it is...)
I am also a big fan of Arvo Part choral music (my personal favorites are "Orient & Occident", "Miserere", "Magnificat", and "De Profundis", and some of the more recent recordings of the Berliner Messe). I find his music to be both beautiful AND intellectually stimulating though one has to be able to accept listening to unabashedly religious themes (a good deal is in Latin but there is no mistaking what it is...)