Recommendation for an audiophile speaker cord that is not "bright"?

A friend has loaned me the Nordost Valhalla I and II as well as Nordost Frey 2 cables. They are wonderful speaker cables but do emphasize the "brightness" of my system including my Wilson audio Sahsa 2 speakers.

Any suggestions? Would used Transparent cables provide a richer bottom end? What about Audience Reference?

Any recommendations would be greatly appreciated. - Thank you - Gerry
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I'll add a third recommendation for Analysis Plus Cables . In searching for cables I first looked for a company with Proof of function and genuine science and engineering . And yes, I was impressed NASA chose their speaker cables for a special project they had .
 After that I saw AP's solo crystal interconnects were most highly recommended and their silver oval 2 speaker cables as well as the larger big silver oval speaker cables had highest approval . I do not find their silver speaker cables bright with my open baffle Spatials and the solo crystal ic's are just magical . That does it for me . I cannot imagine better than what I have now for cables . BTW , balanced connections with XLR are the future of high-end sound , IME . Pro level . I don't believe in using cables for tone control .
Best new price can be found here :
cguitargear777  vendor on EBay    Used can also be found in the usual places .

"There is complex interaction among amp/speakers/speaker cable. "

Nothing complex about this, it is all about opening up so the amp can breathe freely. And there is only one way to do it right, hook up some thick solid core copper conductors..
  How much is enough? No power-conductor on the secondary site should be less than 9awg on smaller systems, 7awg on a fullrange system. Bi- and tri-wiring opens up a good system quite a bit.

OldHvyMec, you`re on the right track with your thinking. 
And your reasoning for 7awg?  ... any idea the resistance of a voice coil? How about the variation from one speaker to another?  Does length of the run come into play at all?

This is hand waving with little to no justification leading others astray.
What’s up with all these “scientists “ recently posting on Audiogon forums? Easy to spot: zero feedback on AGon, and brand new accounts. And same pseudo science rhetoric