Which component is most responsible?

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??