I’m in a similar situation than yours. My library was big and contained tracks compiled in the last 12 years, all of them carefully tagged and categorised.
I was asking because apparently, although the SC5000 have great connectivity in terms of USB ports (including 2xUSB 3.0 ports) and the Prime4 has a drive bay built in and Denon recommends 1TB SSD drives, 65,473 tracks are too many.
From the Denon webpage official FAQ:
We recommend limiting the total track count to under 10,000 songs on a media source. Larger track counts may affect load/search/sort times. We recommend that you only add songs to a drive that you need for the show/night/tour.
Note that this is for SC5000, I don’t know if it will apply for the Prime4.
My library initially had about 50k tracks and although it worked, searching tracks, navigating between crates, albums, artists etc took about 6-8 seconds per action. ie: you are searching one song, each type you type a character you need to wait for 6-8 seconds for results. Same for navigating between albums, etc.
After some research and experiments (bought a better Samsung SSD drive, bought a better SATA to USB3.0 adapter, tried a different folder hierarchy in the drive, removed audio tags that were not stricly needed, etc) I ended up trimming my library to my top 10k, as I found that with 50k tracks it was excruciating to use (although it worked).
I opened the thread " Sluggish library browsing with huge library" were I carefully documented my experiments and my findings. The forum user @ JonnyXDA has made some reverse engineering on the db files and has found a plausible explanation of the behaviour related on how the db is implemented.
I hope this will be improved or that works better in the Prime4. To me, getting rid of a laptop is not about having a loop slicer and a sync button, but about a having a searchable and navigable huge library at my fingertips. I understand not every user has the same needs - that’s just me.