Well, SACD have response up to 100khz. The only argument I can see for that being of any use is if the 100khz sound wave interferes in some perceivable way with audible sound waves...

That would be pretty easy to test. Just make a short file with no information above 20khz, and then make one with tons, see if you can tell any difference. My headphones go up to 120khz or something silly like that....