Poll: Most impactful component

I agree with Roxy54 in the Preamp being the Soul....   my most dramatic upgrades have been preamps .  A good pre is crucial to great sound.   Yes there are some DACs that function as a preamp , some very good ones , but I really think there is no substitute for a great preamp.  

I owned a Zesto Leto preamp ,  amazing piece of gear. I had it for a year and it killed me to sell it .  Putting it in the chain felt like I upgraded my whole system.

 I am having a DHT preamp built,  I sold the Zesto to fund it and am now using a 30 year old SFL-1  temporarily and it was a major downgrade .   Still sounds good but that Zesto was revelatory.   

They all might in any given case.  It takes an entire system to make music…..source, amp, and speakers.  The rest is secondary. 

The answer depends on the system.

My system is balanced and optimized, with all components compatible and at the same level. So, there is only one answer, upgrade my speakers from Sonus Faber Amati traditional to Sonus Faber Lillium. While the Lillium are a bit big for my relatively large space and would cause bass loading at high volumes… I don’t listen at high volumes. So this would make a big difference. Other component upgrades not so much. 

Of surprise to me, power amp has consistently been the biggest difference maker in my journey.  

My room. Whilst I'm grateful ful I have a dedicated room, I know it is too small for what I want to achieve, so I have to live with compromise despite room treatments