Purrin: Thanks for the overview. That is tempting me to get an OR5 now.
I had a similar experience with the Resonessence Invicta: It is a more precise DAC overall, but doesn't seem to have the overall listenability of the M7.
Different (and likely improved) sound should be the reason for Audio gd to replace SA-1.32 with NOS-1704, forfeiting in the process the USB input and the over 96 khz capability.
I posed a version of your question to Audio gd and got the following reply from Kingwa:
"The NOS-1704 have slight different sound to the SA1 even it setting at any modes. The NOS 1704 have a bit smooth sound than the SA1."
I'm a bit confused here: NOS DACs can accept high bit rates unless there is a limit in the S/PDIF or other inputs. Maybe he is using the DIR9001 in it? I wonder if it can be ordered with the WM8805 instead for 192k. I might have to ask him.