OP: What is the most overlooked consideration? Don't believe quality components and room acoustics are the most overlooked. Most here drilled down to exactly that, most overlooked. Overlooked not the same as most important.
We've all been caught, confirmation bias leading us down a road only to discover "wrong thing". Thought my DAC or preamp were experiencing a 60Hz ground loop. It was the ceiling fan downstairs humming away. Overlooked that effect. Doh!

