I haven’t made a direct comparison of a Uniti with an Atom, but I would not automatically assume that the entry level Atom outperforms the full width Uniti player. Can you take your Uniti to a dealer and compare them?
What I would say is that the new streaming platform on the Atom works well, and has a number of advantages over the old one in terms of functionality. I’ve been very happy with mine, using N-Sats. I haven’t tried hooking up my N-Sub yet, although it should be straightforward to do this, and you have the option of using either the low level connection from the Atom’s pre out, or the high level connection.
Good luck!