Which power cord more important?

R1g,
The weakest design is the one depended on PC or interconnect quality.
The small manufacturers of audio equipment hide behind "clarity, transparency and simplicity", but in fact filtering and delivering clean power on the component level seems to be quite complex especially for the amatures.
The bottom line is that there's quite a number of devoted and hobbyists along with business given to more 'enterpreneurs' in high-end audio market with cable business in particular.

You should try to demo before you buy. I just demoed over a three week period a shunyata diamondback and a ps audio perfect wave ac10 on my Plinius 9200 integrated and my Naim cd5i-2. All i can say is, both these cords did nothing for my system. Maybe they needed more break in time but, i could not keep them any longer, i had to return them to my dealer. I am not saying power cords don't do anything, it's finding the right one.

Get one you can afford and try it on the cd first, then swap it to your amp. Leave it where you like it most. I suspect you will hear more improvement, depending on the geometry/connectors/conductors/connections on the CDP.
Ps

Thank you all for your replies, when I finally get around and buy one, I'll be very curious to hear the results...so far I'm a bit of a sceptic but would love to be proven wrong :-) ...

I've found once both ends of the chain are accessorized properly, the middle can stand some looking at too.

My exp does say either and both ends. Which ever is first is first. So what? Pick one and go for it!

Out of pure coincidence I put some onto the amps I had at the time. Then my source got one added to it. Then I added a passive power filter. Then a power cord for the filter.

Then I changed things and did it all over agin, but differently.

Where ever is just fine. Amp first? Fine. Do that.

Eventually, all the ingredients are in the pot, right?

The supply cord to the filter is as key as anything else though. It's 'flavor' will be introduced into anything downstream of it. So in effect, the effect on the amp and it's sound is the combination of it's directly connected power cable, the filter or device to which it is connected, AND the supply cable feeding that filter.

Cook for 200 hours minimum if new, 100 if used, season to taste with software .... feeds reserved seating, and standing room only, as a rule.