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

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.

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.

I really like Raven Audio power cables. All their cable are very well made at a good price.