Power cable education needed

As far as the power cord, I don't know what they bring. Certainly, you need one that is big enough to supply the current needed. An 16 gauge copper wire is rated for about 20 amps, way more than any consumer grade amp. In fact, your electrical panel breakers are probably only rated for 15. Also, a shielded cable can block RF noise, but only for the length of the cable. It won't do anything about the noise the line picked up from the power station to the outlet you plug it into

the really expensive ones are truly truly excellent at emptying the owner’s wallet

like everything in this pursuit, read up, find reliable sensible respected sources of info and equipment, beware outlandish claims and prices, do limited trials you can comfortably afford to help yourself decide, use common sense

It won't do anything about the noise the line picked up from the power station to the outlet you plug it into

Yup.  Which is why money is better spent on an isolation unit like the Tripp Lite IS500 I use for my audio system.  Nothing like a big fat toroidal transformer to clean up the noise in your input power. 

Power Cords are awesome but i dont thimk you will benefit because the Marantz is too to allow you hear a difference 
Your system deserves a proper preamp. You can get one with home theater bypass and still use your marantz for cinema. 
I used to have the av8802 and the multi channel McIntosh, getting a proper preamp was a game changer. 

People that claim to hear a "difference/improvement" with a different power cord are deluded. The sound of an electronic component starts with what comes out of the power supply. Not with anything before it!