Yes, the Oppo will pass 24/192 DVD-Audio (even though it should be protected PPCM) via the digital outs. I have a thread elsewhere that talks about it; Oppo states (in a few emails, one as early as Jan 2008 commenting on the then 980 ) that although the mediatek (I think that's the chip) is supposed to down rez it to 16 bit to protect the DVD-A standard it doesn't with this batch. (make sure you have HDMI off, resolution set to at least 720P and LPCM set to 192k).
However, your comments "So, if I download some high-res 2-channel tracks, throw them on a DVD-Audio" is confusing. IF you download anything but a MLP ISO image you won't have true DVD-Audio you'll have PCM (FLAC, wav, etc) which can be burnt to a DVD, but it ain't DVD-Audio. It's hirez, but it's not DVD-Audio (just making sure we have nomenclature here). If you find ISO images that are true MLP DVD-A rips you can do so with DVDFab 7 or Imageburn if you know the layer break, etc (via the corresponding INI file, etc).