I didn't mean to suggest the streamer in the MPT8/MPSX is bad (subpar) in any way. It is very good and many would be happy with it. The playback streamer + the digital processing/buffering + reclocking in the MPTs/MPSX together ensures very high quality SQ when streaming. But as a few have experienced, having an external high end streamer sounds better - i suspect in some of these high end streamers, they (1) do a great/better job dealing with the incoming noise/jitter on ethernet (you are paying for that); (2) optimized (in some cases custom silicon) streaming processing resulting in lower electrical noise floor and lower jitter (again you paying for that too); (3) the 3 layers of buffering/reclocking that happens (external streamer -> mpsx/mpt8 -> mpd8) helps to improve the overall SQ.
I don't use an external streamer. I use the streamer in my MPT8 to explore music to ultimately buy in CD/SACD form. My primary use case is the CD/SACD transport. I have consistently found playing a disc to sound the best. And in one of my email exchanges with Andreas he did suggest that CD/SACD or playing off a local file sounds a tad better than streaming off the network. To my ears, I think CD/SACD sounds the best (caveat, i have not invested heavily in networking treatments to improve my streaming chain - perhaps that might change my perception).
I have heard the MSB reference (though not side by side and so subject to the unreliability of my aural memory and differences in the downstream components) at a show. It did not have the MSB digital director (for source isolation and additional processing) and it had a CD transport as source) The MSB sounded very smooth and organic. But I find the MPD8 sounding more natural (in tone) and an overall increase in presence of the performers (i have a newer MPD8 with the latest output stage that was released starting in the Sept/Oct'24 production run, and that might be a contributing factor) .