Wish I had put more emphasis on cables earlier

Welcome to the club

Good cables can enable us to realize the potential of the entire system.

Testing in reverse, going from really good cables back to mediocre ones, with lower grade purity metals and poor shielding, while moving them around a system to compare differences can be reconfirming.

Evaluating source components and evaluating speakers with low grade cabling throughout a system can be a great loss of time and less than rewarding experience. I also place a value on cables when the rest of the system and speakers are high in quality. Low grade cables can mask the potential.  ...only as good as the weakest links.

With regards to power cords? How relevant can it be if the a.c. wire from my home fuse box to the outlet is not thick?  Would the amp be most affected by the power cord upgrade? Other than that and my dac, can't change the power cord. 

I take it you're just a BIT resistant to advice on cables? How long do you want to take to figure out power cords?  Five years? Ten years before you try?  :(
EVERY power cord is critical!

Yeah. Hate going down slippery slope since this hobby can get really expensive. Haven't really shopped for power cords but are there some reasonably priced ones worth recommending?