Make sure you listen before you buy, and be sure these are the kind of performances you want. Because although other reviews rave about this, I remain unconvinced.
Mind you, these comments only apply to the first of the two CDs. I haven't heard the second and can't comment.
But I was taken aback by the interpretations on CD1, some of which sound positively Victorian - slushy, wobbly and tonally wooden. And there are some vocal infelicities that simply should not have got past the editing process.
Take the Mozart: even in the first two bars - just the instrumental intro - there's a slushy rit (the first of many!), a sudden accelerando and another rit just before the choral entry. Where does Mozart ask for this? It might have passed muster in 1890, but in 2007 it sounds extraordinarily dated.
There's a lot of swooping (eg 'ave verum corpus' at 15 seconds in). The vocal entries are tentative and the ensemble is patchy: at the end of the first vocal phrase (20 seconds in) they don't come off together. Listen to the 't' sound of 'natum' at the start of the next phrase (26 seconds): it goes 't-t-t-'. At 'Vere passum..' the singers are sneaking in because they're not sure of the beat, so there's no positive 'v' sound to 'vere'; you'll hear this 'sneaking in' repeatedly through the whole CD - a sure sign that the singers lack confidence in the conductor's beat.
At 1' 50" there's another rit (not Mozart's!), and again the entry is ragged and ensemble poor (listen to the 's' sounds of 'esto' and 'nobis'). The strings (and these are good players) sound deeply uncomfortable with the tempi and with all these rits and ralls. This performance is molto maestoso, vibrato-laden and sentimental; and - I'm sorry - but choir and players are simply not together. And I find that repeated in the other tracks.
Perhaps I'm a detail freak. If none of the above matters to you, then go right ahead: the pieces are some of the great works of the choral canon, and if you enjoy them done this way, then go for it.
But be sure you listen so you know what you're buying before you do.