Best place to install power cable

If you had only ONE aftermarket/quality power cord where would you place it in the chain ..1/source(CD player)..2/preamp...3/power amp..4/from wall to power supply..and why?..Please no "try them and see what sounds best"...thanks
In my experience, the two components that seemed to react the most positively to the "right" power cord upgrade were my transport and amp.

In my case, the amp benefited possibly because it was the only component connected directly to the outlet. My reasoning was to find a power cord that worked well with my amp and utilize it in a way that didn't restrict the amp dynamically. I've never liked the way amps sounded in my system when run through a power conditioner or strip.

The other place I've put my better PCs were between the power strip and the wall, so that the rest of my components all received the benefit of some sort of shared reduction in PC compromise.

Does that make any sense?
My first choice would be the Power amp, simply because it draws more current than any other electronics and a well constructed Power cable will better handle that current than a stock grade cable. Now, if you have a power conditioner, I would connect the power cable from your outlet to the power conditioner and plug your amp into the conditioner. You also should consider that a power cable composed solely of copper will have different sonic qualities than those composed with silver. On my transport, power cables composed of silver tended to produce very bright sonics. I think Gunbei has offered up some solid advice.
The bets cord always goes on my source (CDP).
I would try it on all your components and decide where it works the best. If you don't hear a significant improvement somewhere, you don't need it.
In my situation, using all Lessloss power cables, my preamp/dac provided a better place to put the pc, than the APL Denon 3910 that I use as a transport. But it wasn't until I added two pc's to my Nuforce 8.5's(version 1), that a synergy occurred.
Source first amp last.
Ditto Jdombrow
Biggest difference usually is with the cd player, use your best cord here.

My experience is that not all power cords are designed the same, factors of gauge measure, etc., affect their optimal application. Some cords work better with high current application but not the other way round. That's why you see certain designers have different models for different applications, Michael Wolff and Chris of TelWire coming to mind. Given a choice I would start with the source, meaning cd player, transport, dac, etc.