We all agree, I am sure, that none of us should blindly go buy an HD621 without hearing the difference it makes first. A dealer test is the only way to decide if it is right for us (with our ears, our system, our room, our taste).
Using SACDs converted to 24/96 then downsampled has the disadvantage that you are starting with something which is only sort-of-hi-resolution (leaving aside the hype). The information above 20kHz on an SACD suffers from high distortion, and this technical weakness was discussed by Gerzon, and I believe referred to by Meridian when DVD-A was being first publicised. DVD-A has no such weakness (though it has other practical and licencing ones).
You didn't read my post. I did it on SACD, 24/96 Native Flacs and 24/96 Bluray.
If "downsampling" is "bad" (As you are implying) then it should be even easier to hear the difference (how much the sound is degraded), the point is I don't. So why will I hear it going the other direction (which will be even less of a difference, because it won't be true hi-res)? And what I'm starting with won't be damaged by a downsampler.