Re: CD, SACD & DVD-A
A short note: my comment about optical media degrading over time is only true for CDs we make ourselves (i.e., blank disks we burn in our PCs). Commercial CDs you buy are made by mechanically pressing metal disks and coating them in hard plastic, and they do NOT degrade over time (unless you scratch them so much the plastic becomes opaque, anyway).
Also, I was under the impression that HDCDs, however they may have been recorded, are still only 16/44 standard Redbook disks, but I am uncertain of this. At any rate, if they do have higher bitrates, your PC won't capture or record the added detail if it's CD recorder is not also HDCD-certified. The specs must carry through the entire equipment chain to maintain the quality you seek. Any lower-level component in the chain drags the entire process down to that lower level.
"I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone."
— Bjarne Stroustrup (creator of C++)