Which component is most responsible?

Turn this one around. If you have a system that already convincingly separates a choir, what component could most easily destroy this if replaced? I would be tempted to say recording first but the truth is any sub par component in the chain could blur the choir. In general, it is the weakest link, not a certain component category, that limits the capabilities of the system. IMHO.

Bill

Speakers, and for me only those that are time and phase coherent, which means Thiel, Vandersteen, Dunlavy, Meadowlark.

An owner.

Assuming a competent (or better) recording, I vote for the room as the component that can do the most harm to the sound.

Preamp