The cheapest option was to use an existing cable, made redundant by the 20amp connector on the ARC. I use Sablon Audio and Lessloss, both of which I find excellent. Mark at Sablon popped a 20amp plug on an Uber Robusto for me.
I am not sure I can instantly hear the difference with power cable changes, but there was with switching the stock ARC cord with the Sablon. An instant increase in macro dynamics, it sounded like the volume had been turned up and crisper, clearer treble. A very worthwhile difference. I have'nt tried anything else. I would have tried Shunyata if this modification had'nt been available. Thanks again for the help