Re: "a brave person who said that HRA has no audible benefits"
Just because something says SACD or DVD-A on the label doesn't mean it was mastered as high-res audio.
Back in the early days of vinyl, I know for a fact that some CD masters were recorded from vinyl copies.
Record companies tend to be cheap and nasty, and the likelihood they'd consistently make a special effort to get the very best from high-res media isn't high.
At the very least I'd have wanted to see some word length analysis to check that the supposed high-res content was actually there in the first place.
A more realistic test would be to record high-res audio with a clean signal path to master recorder, and then run that through the A/D/A system.
As someone who has spent a lot of time listening to converters, I find it amazing that it's apparently impossible to hear the effects of a mid-price A/D/A converter at all, never mind the source. Unless you're in the professional bracket (PrismSound, etc) most converters really don't sound that transparent. And I know from experience that the difference between a 24-bit master and a downsampled 16-bit master is absolutely and reliably audible.