What is the most overlooked consideration?

+1 properly treating the room

The perception of timbre can indeed be influenced by room acoustics—through reflections, absorptions, and resonances that may subtly enhance or diminish certain frequencies. However, these effects are generally minor compared to the intrinsic harmonic content of the sound produced by such components as a DAC or preamp.

Therefore, I respectfully disagree with the assertion that timbre is an acoustic "concept" that can be rationed by the ASW/LEV ratio. To illustrate this, consider a simple experiment: move from your main listening position closer to the speakers, thereby minimizing room acoustic effects. You’ll likely find that the fundamental "color" of the sound remains consistent, reinforcing the idea that timbre is predominantly determined by the source and its harmonic structure.

For example, in the recent (2025) DG recording of Bruch & Korngold featuring Bomsori Kim, the violin’s timbre is authentically rendered through my Topping D90 III Discrete DAC. In contrast, when using a more affordable AKM-based DAC, the violin’s sound becomes warmer and less engaging. This comparison underscores how a DAC handles the harmonic contents in the conversion process could significantly impact the perceived timbre, beyond the influence of room acoustics.

Never thought I would say that, but power management is a key consideration. Outlets, power cords and power plants can transform the sound of a system. I was very skeptical until I experimented with them. No need to go nuts, however. Just need clean stable power. Similar experience with external power supplies vs internal ones.

Buying equipment you can buy, try in your listening room with your equipment with the ability to return for no or little money if you’re not happy.  That involves Customer service and warranty.  I see so many questions online after people have bought equipment and can’t get help from the manufacturer or are looking for where to get gear repaired.  

Very interesting and thought provoking answers. It’s a way the Audiogon forum can actually help, by sharing ideas, solutions and opinions. It is possible that threads do not have to be filled with arrogance and personal attacks. For those who have a complimentary stereo component or accessory the WAF is another overlooked consideration. No offense intended. Offered by @aewarren and I am in agreement.