dCS Rossini - separate streamer req'd for best sound?

About to pull the trigger on an Apex Rossini, and have questions after the audition. Mosaic could not compete vs an external hardware streamer source for the Rossini in SQ. Should I expect to have to purchase a streamer to get best SQ? Also, the Rossini clock is a major improvement and I’ve already included that in the list to order. Anything else I need to consider that will make another very large dent in my wallet before I dive in?
When this thing is firing on all cylinders it’s one of the best sounding dacs I’ve heard. Just seems that a lot needs to fall into place for that to happen.

So far (got Rossini Apex delivered 1.5 week back) I have tried following options (My music server is Naim Uniti Core) -

  1. My Naim NDX-2 used as streamer and proving input to Rossini Apex through spdif connection
  2. Using Mosaic with Roon Core running on Mac Mini (Roon Core only does music management and directing music from the server to Rossini).
  3. Naim Uniti Core directly feeding music to Rossini dac in spdif

All options sound mostly equal with option 3 being the best so far.