One Cord To Rule Them All

I'm thinking about a Cullen cable for a Furman it 20 I powering two monoblocks but I only need a 4' PC. His top model is only around 350 

I think no way you use 600 watts other than maybe for a fraction of a second if you turn everything on all at once. 

A used Synergistic Research Master Coupler is right in your budget range. Big, bold, detailed and very well balanced. There's a reason they sell used for about what they went for new 30 years ago.

If your $5K "power regenerator" is going to regenerate the power anyway, and then you are going to run other power cords from the regenerator to the equipment you plug into it, then why not just use the largest gauge copper power cord that delivers current to the regenerator?  Your 9 awg Pangea AC-9 cord should be plenty large enough. I would be more worried about what is coming out of the wall.

I know some say it doesn't make any difference beyond a certain size but I have found otherwise after constructing power cords from 10 awg NOS WE wire and Furutech FI-11 connectors using 6 individual runs in a star-quad configuration - so an aggregate of 7 awg to each the load and neutral (and same to ground).  When run from dedicated 20A lines to my large monoblock amplifiers, the difference was a noticeable improvement over 10 awg Oyaide TUNAMI V2 power cables.  You can get basically the same cord from TRL as their Seven Plus - American Series, which is made from (you guessed it) pairs of NOS WE 10 awg wire.  I believe they braid rather than twist the wires (tomato-tomahto). 

What gives you the impression the P10 needs a "better" pc than the already better than stock pc?

Power cords don't "pass" wattage. 

Just my experience-I plugged a $25K+ Nordost Odin II into my PP which normally is a Heimdall II. No angels singing/rainbows. The PP just did what it  normally does. I also did Nordost Blue Heaven vs Heimdall vs Pangea AC13Se=no noticeable difference.