Mike,
first of all, I ignore what an UC2 is – sorry, I apologize. Second, I specified that my new XS-2 has integrated a bare CDX2 and Ovator S-400s in my listening room, which proved difficult for years and has made me change more than 40 times some piece of gear from cables to speakers to find something resembling peace of mind. So I sincerely don't feel like giving you any generic opinion or advice about a standalone XS-2 in your system. And I am somewhat conflictual about Totem speakers. All I can say is that the XS-2 has almost the driving capability of the SN1, more finesse, a much more organic and flowing voice, manages inner details in a way I hadn't yet heard in a Naim amp, has a wonderful balance between body and clarity, has excellent dynamics and is more 'mature' than its predecessor.
My opinion only.
Max