Which component is most responsible?

Speaker setup and room acoustics mostly.

Assumption is rest of gear feeding this is decent quality and matched well.

In this order: speakers, preamp, amp, source components, cables.

I appreciate all of your responses thus far. I'm beginning to think the weakest link is my speakers. I recently went from a solid state amp to a pp tube amp that opened the soundstage and provides a tonality in ways that it will be very hard to go back to a SS amp. However, I think my Polk LSI15’s are limiting me in achieving distinct separation of voices in a chorus. My front end consist of an Oppo with a Monarchy MN24 DAC, which is a very organic. I alternate between the internal Preamp in the Monarchy and a passive preamp. I don’t think the electronics and source are the culprits??

FWIW, separation of voices in a chorus is very difficult to achieve UNLESS it is in the recording in the first place! And it usually isn't, at least in my experience. Be sure you have a recording that really has the distinct separation of voices you are seeking. The clarity that you seek would also be apparent in the 'soundstage' presented by an abundance of recordings and would not only be apparent in the separation of instruments. That is just a starting point. Once again it is clarity of individual tone as well as location of the instruments.

I can not comment on the performance of your Polks. I've never heard them, but that said before I decided to ditch them I would be sure I had them, and my room, optimally set up so I could tell if they really were deficient or if it was just premature up-gradeitis.

Newbee, perhaps you could suggest a suitable recording to the OP that you know has a good separation of voices. That takes the recording variable out of the problem.