Power cable Advice...

That's a pretty big jump from stock and quite a large budget dedicated to AC cables.  Just something to think about is that you can make your own cables for a fraction of the cost and have more control over experimentation with what works best for your system.  There are endless debate on plating materials, cable design and even shielding (such as whether to ground at one end or both).

As an example, Supra's SPC 2.5 cable (silver plated copper) terminated with IeGO's gold plated copper plugs and shielding grounded to the mains side is an excellent cable and will be a tangible improvement over stock.  Material costs are maybe $150, at best.  Heck, you can even start with Viborg's plugs and see the different effects first.  If you like the combo, you can go all-in on more exotic cables and plugs.  Personally, I opted to add voltage regulation/power conditioning over pre-made exotic cables and happy with the results.

You cannot do better at ANY price than a Cerious Tech Lumniscate cable. it runs about $1599 but there are deals from time to time - particulate if purchasing multiple cables. Lumniscate cables complete transformed my stem and were if particular benefit with my digital gear and preamplifier. You will thank me later. A hidden "gem in the rough." 

Newsflash: it doesn't matter. I'm drowning in snake oil here. If someone wants to spend a ton of money simply because they want a pretty looking cable, great, that's their business. But let's not pretend it's going to make anything sound different. We should be helping people here, not enabling the dark side of this industry. 

I'm thinking of going from Mackenzie interconnects to Earth between my amp and pre. Do you honestly believe it is all snake oil and any difference I hear is the placebo effect? But then we are talking about audio and not medicine so isn't the placebo effect worth it?

Nordost states in it's packaging that the "Power Cord is the most critical cable in your loom".  I was running Ansuz cords which was my first upgrade over stock cables.  Big difference.  Upgraded to Shunyata sigma v2's.  A huge difference.  I gifted my Ansuz cables to my brother, who replaced his stock cables on his Mac gear with them.  He called me so excited, saying he couldn't believe the sonic difference the upgrade made. 

@squared80 Newsflash-It DOES matter.  I have a very revealing system.  If yours isn't, perhaps you can't hear the difference or perhaps you never tried.  If so you are depriving yourself.  The Cable Co has a library of loaner cables, give it a try. You have absolutely nothing to lose. Then please report back with your findings.