Hi Rudolph,
On a Lampi I am not totally sure at this point. With the original dsd engine and importantly PCM engine, I found the delta between the 2 large and thus upsampling to dsd was the way for me back then. When the PCM r2r versions appeared, PCM was profoundly uplifted and virtually on a par with some dsd (not obviously the great dsd recordings that are virtually unparalleled in digital IMHO).
That said, having spent a lot of time now reviewing the SGM server with T+A dac, I can 100% say that the performance of the T+A is monumentally uplifted versus no SGM - this was all @ 512. Tidal to 512 was very much an experience.
Alas I was only able to upsample to double dsd on my GG due to an issue but my GG returns today with 512, just a shame the SGM is now back with new owner. The SGM to double dsd on GG delta was less than the SGM to T+A delta at most rates - i.e. The gains with upsampling on T+A were much larger than the gains on GG.
The technical question for me is whether there is something about different dac topologies that lend themselves more happy to powerful upsampling versus native. That said, whilst other reviewers have stated the r'aison detre of the SGM is the ability to upsample to 512, this is IMHO nonsense. A great server like SGM can perform very well using much lower sampling rates or none. I know of some Total Dac customers experiencing tremendous gains with SGM but not upsampling to high rates at all.