What is the most overlooked consideration?

This is by no means the primary consideration, but as a retired person on a comfortable but fixed income, one of the things i always consider is whether a component is desirable by others and can I purchase it for a good price. Can it be flipped quickly, without losing money or at a slight profit.

SYSTEM synergy

It may be hard to define in words, but you know when you have it (or lack it.)
A newly selected audio component inserted into your rig can create an audio performance change now ranging from poor/non/optimal to good/ ​​​​​improved.

Think all the daily AGON forum posts asking for new components recommendations.The conflicting responses range widely and all too many simply reflect personal fave bias.

Just because a touted Brand X component seemingly works well in a Respondent system, is no assurance that it will succeed in OP’s system.. “ One size does NOT fit all”…

All the things previously mentioned are considerations, I also need to see quality parts, I also much prefer point to point wiring in pre's, amps, speaker crossovers, power supplies extremely important.

A mis-match of the preamp and the amp that can hinder the overall performance.

@2psyop 

My top criteria’s when choosing a gear; does it provide long-term musical connection. More importantly, does it invite me to play more music, not just “audiophile tracks”?  Secondly, synergy and lastly designer’s (manufacturer) integrity and accessibility; if and when I need the support of the person or team behind the product. 

I have gone through my fair share of components in my pursuit of putting together an audio system that connects you to music intimately. A good audio gear doesn’t just sound good, it changes your behavior; how you feel and appreciate the music. 

Reputation matters but resale, it’s a crap shoot :-)