HD621 should ALWAYS upsample on everything.
Agreed.
It's not worth the trouble/gain of running audio through HD621.
Almost all my important audio sources are mch HDMI, anyway.
Only combo that doesn't work optimally is a combo unit (e.g. Oppo over HDMI into HD621->861V6) when playing a CD. If you have the bucks for that get another CD spinner (easy to equal an Oppo for CD or just about any Music Server for that matter).
Server goes direct to 861 but the Oppo/Sony/Ayre players go via the HD621. Perhaps that will be modified when my v6 arrives.
So with that said, who cares what the source data rate is.
Because I need to know about what the players output in order to report it to readers who care because they, right or wrong, want to base purchase decisions on it.
Kal