Power cable for REL sub -- modestly priced

Does anyone have a suggestion for a longer cord for a REL 328 sub? It has a class D amp.
Before you suggest high dollar cords, please know that I'm not a skeptic, but am tapped out for power cords. And, for what it's worth, I had a Pangea AC9 1 meter power cord which I experimented with using my REL. Made zero difference. In fact, in an exchange with REL, they said this: "A while back, REL tested some third party power cords with our subs but did not find a noticeable impact."

So, my question is about a decently made but not pricey brand of extension cord for a REL sub. I'm not looking for Shunyata etc.  Any suggestions? Thanks.
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I do have a pair of Rel S510 and other 
Rels in the past and cannot recall 
hearing any difference with upgraded 
power cords.
I think it has to with class d amplification.
 I am currently using Pangea power cords
with my Rels.
 $$$ owerades cables do do nothing....And for a sub even more so, if there was any interference. it would be at the high end and well you are talking about a sub,,,,If your sub turns on your good
I own a pair of REL Gibraltar 2's.  These have 450W AB power amplification and they do and have reacted to different power cords.  I have had Cullen cables (decent!) high end Synergistic Research (better), Audience (OK) and finally have found a very reasonably priced "Pro Audio" pc made by a Swedish company.... Vovox Excelsus. (best) at $400. for a six foot cable.  A bargain by audiophile standards.  Changing power cords, atleast in my rig, really defined and helped me understand bass bloat and overhang.  I can now hear true taunt bass, actual notes not some boomy representation of bass....get rid of the overhang and the micro details in the mids and HF are more clearly defined, so it really cleans up the entire presentation.   YMMV.  
@ptrck If mine wasn’t class D, I’d probably be much more inclined to buy cords -- as I have with other gear.

FWIW, nice new video on how to make a cable by Tarun A British Audiophile: www.youtube.com/watch?v=gfVYfC6tmcc