Micro,
why are you looking to transcode from PCM to DSD when dCS supports also DXD?
Seems you would be transcoding from PCM to DSD and then using DSD over PCM to transfer from PC to dCS (in theory should be transparent but still overheads and complicated by the software solution on the PC).
Upsampling is ok as long as it is same multiplier (that was PMiller's view anyway but a nono if it is not), appreciate this becomes complicated when some recordings are 48khz multiplier but dCS supports DXD at 352.8 and 384k.
I guess you can compare both, key for DXD upsample would be choice of selected filter in the Vivaldi to be as close to ones preference, but again not sure how much of this relies upon the Vivaldi Upsampler box.
Would definitely be interested what the results are from your auditioning as it will be interesting.
Cheers
Orb