Best Power cable around/prefer under $300....

I bought Pangea SE cables, most used and discounted, and saved hundreds. Knowing they're better than stock cables but not exorbitant just crossed the question off my list. Some people go back and forth and compare PC's but most of my comparisons have not revealed much of a difference once I moved past stock cords. Just my experience.

I'd recommend looking for used Cerious Technologies Graphene line of their Blue, Red, or Yellow power cords, assuming you can find them in your price range.
Although you did not include the following power cord, I also believe the old original Synergistic Research Reference A/C Master Coupler power cord would work very well also.
Another option: Soniquil Power Cable by Raven Audio.
1.5/M $184
2/M $224
3/M $274
Very well built and huge bang for the buck!
https://www.ravenaudio.com/product/power-cables/

I just bought two new Silnote power cables off of Audiogon for my Parasound amp and pre for $100 plus tax each.

Cerious GE, Transparent High Performance

If you decide on giving  Nordost a try, Blue Heaven is the way to go. The power cord shares the same construction of the Norse series(Heimdall).

Obviously, it's scaled back just enough for the price point. Best buy for new Nordost users.