Are manufacturer AC cables good enough?

No manufacturer is going to hobble the performance of a product by supplying a sub-par pc; after all, the goal is to sell the product, and they know people will check it out beforehand (or at least most people will).

But... in the "lower" range of HEA, it's all about price point.  So that's a factor.  And as you move up to the "higher" range, manufacturers know that the buyer will almost certainly want to use their own flavor of pc, so what's the point of including an really expensive one.

When the power cord is heavier than the component to which it's attached, you know you've got a problem.

Of course, that's why they invented scuba diving weights.

The same way Nature equipped up with two ears so we'd be able to wear glasses.