As far as latin goes, the skies the limit, there are hundreds of academic quality gregorian chant cd's out there, many of them somewhat obscure and hard to find, but those who collect them or did collect them in the 90's have great collections. Psaltis John Michael Boyer has a spectular collection of both byzantine and gregorian chant cd's (500 to 1000??) that he lets friends and visitors peruse through and listen to with permission.
Most university librarys that have good music schools have excellent selections of western chant cd's too.
However, as for English, I have come to the conclusion that there needs to be made a professional recording of the Office or Mass with english language gregorian chant sung well and as it would have been at least before the reformation (if not before the schism itself).
Dr. William Renwick is someone who'd be very happy to help produce such a cd. I suspect Capella Romana would also have an interest in this. It's reaching a point where this is an important step for showcasing a respectable and mature Western rite liturgy, as the hundreds of english language byzantine rite chant cd's have done to expose many to the Byzantine liturgies.
There's been english language chants recorded by anglicans over the years, but I'm not aware of a single cd that features it properly or exclusively, except for one....but it uses a poor translation!
However, here are two examples from the audio cassette that came with it, which I recorded a few years ago (back when the Roman Catholic Church (and many Anglican Churches) used the "intentionally less accurate" 1973 ICEL translations):http://www.amazon.com/An-English-Kyriale-Music-Eucharist/dp/0005992699/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1373416732&sr=1-1-catcorr&keywords=An+english+kyriale
06 - GLORIA V - Salisbury V (Vatican V, PMMS IX) (12th c)https://www.box.com/s/z9xjwqc810xtlzfhp3h2
15 - SANCTUS I - Salisbury I (Vatican II, PMMS I)https://www.box.com/s/nyauqwjom4hkvne4dtkx
26 - AGNUS DEI I - Salisbury I (Vatican XII, PMMS I)https://www.box.com/s/v4nesjbldi4v3kqszfde
The early organum and 2 voice polyphony from before 1300 AD can be especially interesting.
This one is from the 900'shttp://www.youtube.com/watch?v=vGJvzJvqo_c
this one from the 1100's "In praise of St. John the Baptisthttp://www.youtube.com/watch?v=zuMZEvg2fSk
(Musica Enchiriadis, 9th century) - sequence: Rex caeli Dominehttp://www.youtube.com/watch?v=YOMcd-O6Urs
This CD made by Mary Berry showcases even better pieces, though.http://www.amazon.com/Christmas-Royal-Anglo-Saxon-Winchester-Century/dp/B000002GT7
The Rev. Benjamin Mayes, a Missouri Synod Lutheran minister did a fine job singing many divine office hymns and simple chants.
The only issue of notice is that a number of the hymn translations are not the most accurate paraphrased translations, but they're not too far off.
We praise Thee, O God (Te Deum laudamus) Mode III http://www.youtube.com/watch?v=mfSl9or0j3shttp://www.llpb.us/Seasonal%20Propers-Sung.htm