A Samsung 980 250GB would be sufficient, IMO.
With over 250k tracks in your library, then it’s probably not a bad idea to upgrade your RAM to 16GB or possibly even 32GB (I don’t think the standard Nucleus+ has this much).
I would use a matched pair of RAM cards to make up the total (e.g. two 8GB cards for 16GB or two 16GB for 32GB). This thread gives some more information about RAM upgrades…