Power - where to start? Mains, chords, conditioner, filter?

There is some common thinking here among the answers, and I agree - start as close to the beginning of the chain as possible, then work your way down.  At the panel/in the wall if you can, then outlet(s).

If these upgrades are not possible/feasible, the thinking about starting at the beginning is still the same.  Start with the cable powering your line conditioner (or start with actually getting a line conditioner if you don't already have one), then your source(s) - streamer and DAC in your case.
It may seem counter-intuitive to upgrade power cords on lower power draw components before your amp, but if/when you do, the "goodness" filters through the whole system, IE. you will be amplifying a better signal/source.
Good luck!

One of the best investment for me was a PS Audio Dectet https://www.psaudio.com/dectet-power-center/

Maybe this is the appropriate place to ask a question I have wondering about for a while. What is the logic or the theory that enables an upgraded power supply cable to improve a systems sound quality? The power getting to the system is at the mercy of electricity supply company the electrical contractor who installed the switchboard, house-wiring and outlet sockets... It is hard to imagine how an improvement in the last few feet in that power supply chain might make a difference?

How is the Pangea Audio AC 9 MKII? I'm new at this power cable stuff and want something for my Krell Digital Vanguard and Vandersteen setup. Also, is isolating the Amp with a dedicated circuit and the rest of the electronics on a Furman PC a good layout?

Can you explain how this works and where it fits into the system?

From above:  An alternate route to a dedicated power line might be to purchase a YETI power backup system
https://www.goalzero.com/product-features/portable-power-stations/ 

A fellow audiophile just made me aware of this unit
- generates a perfect sinewave
- works just like a UPS
- but with a larger capacity
- handles large transients with ease
- on his system a YETI 1000 will run the ENTIRE system for over 5 hours
- you can leave it plugged in - or not


Also, I thought the power conditioners were supposed to really clean up the dirty power coming through the wall.  So why use a power conditioner if I'm going to upgrade the breaker, wiring, and outlet (which is not cheap)?