AC Power cords, which components 1st...?

I've been lying in the background with regard to upgrading power cords and I'm now thinking that I might give it a try. I fully subscribe to the laws of diminishing returns with the exponential (if not worse) price curves of these products. Therefore, I'd be looking in the $50 - $250 dollar price range. I don't need long cables (3 - 4 ft should work) and that may help the price point. Pre-owned is fine with me as well.
Given that, which components first? power amps, pre-amp, source...? and, any thought on power cord given my predisposition?
Aloia power amps, Casanova pre/pro. Capitole MKII (soon, I hope).
Thanks