Thank you for all of the samples you have found on YouTube. I will be listening to more.
I have only recently started to listen to early choral music. My taste has always been for bigger works. I haven't checked the internet for videos of my favourite performances, paying little heed to their sound quality because I haven't taken the time, some of which are:
Bach, Mass in Bm, Rifkin, Nonesuch
Beethoven, Missa Solemnis, live Levine, DGG
Mahler, 8th Symphony, de Witt, Naxos
Verdi, Requiem, Papano, EMI
I'm also very fond of Mendelssohn's choral music and could recommend some fine performances of it should anyone be interested.