I suspect it’s a JRiver issue. I am a B2 tester, so it’s been a long time since I played DSD over B1; but I do not remember excessively long wait times. With B2 there’s certainly no problem in my setup (NAS running MinimServer), but I don’t use JRiver. Have you ever tried, or could you try as an experiment, some player other than JRiver? It would be disappointing to invest in B2 only to have the problem continue since it’s a software, not a hardware, issue.
Update: I played a bunch of DSD files tonight and paid particular attention to the load times, which I confess I hadn’t thought much about. From MinimServer to B2 via DoP I found considerable inconsistency. Some DSD files took a while to start playing (up to 10 seconds, in some cases) while others were much quicker. There was in general a correlation with file size; big symphonic movements usually took longer than a folk singer with a guitar, but not always. For instance, the first movement of Mendelssohn’s Scottish symphony (London Symphony Live) took 10 seconds, but the fourth movement took only 1 or 2 seconds and it is almost as long as the first movement. I could not see any pattern of songs within an album taking less time than moving to a different album or anything like that. The software programmed into B2 is obviously trying to keep things moving along quickly (sometimes the cover for the next song appears while the previous one is ending) but this did not entirely eliminate slow loading on large files.
Note: I do not have any DSD albums that contain tracks meant to be played gaplessly, so I can’t speak about how well B2 handles such. The PCM gapless tracks that I have work fine.
I don’t know how the use of DoP contributes to loading times. My Synology is a DS213, which is 1/4 or 1/3 of the way up the Synology food chain. In other words, it’s not the cheapest model but there are others with faster processors and more RAM; whether they would give better results I don’t know, but that is certainly possible. And I have no idea what sort of overhead JRiver introduces.