Each to their own I guess, but let me take a minute to digest your logic.
1) You want a kit made O/S by a forum member which in essence is a custom non-proprietry kit as it's not made by Stillen, HKS or Greddy!!!!!!!
2) The kit from the US is 8awg not 4awg as offered by the local "pro". ( btw 4awg is bigger than 8awg if you were wondering ).
3) The US kit has primarily 2 grounds but lots of runs of cable grounding "nothing", just piggybacking around the block. Look carefully at the pics of the US kit and compare to those on the FHRX site. To successfully ground the Alt/Batt/Starter etc they need to run directly to a grounding point on the chassis to be completely effective. With the FHRX kit each run is connected directly to ground.
I just can't visualise the US kit being as good or better than what Marty or any other proffesional Car Audio installer could do for you at the same price point.
just my 2c !!!!