The ridgidity is dependent on the brand. Cardas are not ridged although thick. In general I agree that the emphasis on greater flexibility for components. It is not uncommon this to be true.
Most companies make power cords specifically for amps and also specifically for components. Component power cords are designed for greater noice resistance and the amp ones for greater current capacity.
I recommend just work on one cord… for your amp first. As I mentioned earlier, this typically will make the biggest difference. This makes it simpler. You can use Cableco’s lending library, instead of buying… or have a dealer lend you some. If you don’t get a valuable sound difference out of this… then you are unlikely to get a bigger difference out of one of your components (but it is possible).
Also, when auditioning… well anything. It’s good to do a few quick A / B comparisons and write down the results. But, unless you are really put off my a change, spend a number of continuous hours listening to music (not to the power cord). When you take it out, you will most likely get the best take on the real change in sound. I always switch back to my standard… which over the decades [I have chosen to be DHLabs… to me has always been a good quality budget wire. That is me. You can use Home Depot as your standard if you want.]