If you can get Missa Luba
then do so, it's awesome.
If Hilde VB doesn't float your boat (which is a strange enough idea in itself), then avoid Guido. Dufay might be closer to what you're after; Howells & Fux come highly recommended, but not by me; Buxhetude & Handel bore me rigid, but might be worth looking into; Bach's Passions and masses are amoung the peak of everything, ever; pretty much any great mass will include a fair amount of choral stuff - Mozart's mass in BMin [I'll edit this if I mean something else] is indispensible; Bruckner's Motets are mind-flayingly wonderful, if you can get past their near-impenetrable surface.
Messian or Schoenberg's Cinq rechants/ De Profundis may be 'modern' enough to appeal (although personally I tend towards the earlier stuff). Penderecki's 8th gate of Jerusalem is vastly under-rated, and I suspect Part's Miserere is gorgeous enough for absolutely anyone.
Will likely forget to edit omissions/ errors, but PM me if you want me to up some stuff.
Edit: I may come back with a non-Western 'classical' list of choral stuff and all.