The first classical music (all right: baroque) I ever bought was by the Swingles: I think this may be one of the tracks.http://www.youtube.com/watch?v=vonJhz2COck
What do you think of Palestrina? Many of his works have wonderfully textured vocals which I really enjoy, and which I'm sure that you would enjoy as well.
Re Palestrina - I certainly find it pleasing, but I would have to say that up until now I have not been greatly moved by Palestrina.
@dearieme - I have this on LP - it was a particular favourite of Glenn Gould's, so we are in the best of company. What about this one:http://www.youtube.com/watch?v=sgf0H-X6an8&feature=relatedBrandenberg Concerto 3 by JSBach - the really amazing bit comes around half way when the different members of the group sing each note of an arpeggiated phrase, so the phrase travels across the group from one stereo speaker to the other...
"one stereo speaker to the other": my budget didn't rise to stereo until about 1979.