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

213runnin I think most everyone is saying spend some more money and get some  more cables. 

And that does not a consensus make.  I feel like you're going to insist that it does, so...

Wildly different price points, wildly different design types and brands and... my post was merely a light hearted observation.

This is a seriously disappointing thread. Lots of great and likely somewhat useless wiring suggestions. If you find your speakers "bright", wire is not where you start making changes .... ask why do your speakers sound bright?

- Are you running tube gear or solid-state? If tube gear, the damping factor may be low in the base, especially around 100Hz where these speakers dip to 2 ohms. That could be rolling off the bass making you think the highs are bright.

- More likely is you have an inadequately treated your room for these speakers. Room response makes a speaker bright, not the speaker on its own. Some additional absorption, a carpet, ceiling diffuser/absorber, etc. may be ideal and give you better overall imaging.

I would absolutely try Morrow Audio cables.  They have a very good return policy.  I started with the level 4 interconnects and paid for the burn in.  I had been auditioning several cables through the Cable Co. (highly recommended) and I decided to try the Morrow M4’s on sale through Morrow with a no questions asked return policy.  I was amazed.  A smooth, glare free transparency, while still conveying the emotional content of the music.  Incredible dynamics and balance across bass, midrange and treble.  I was so impressed I returned the M4 interconnects and upgraded my entire system to level 6 interconnects and speaker cables.  At 200 hours these really bloomed and continued to get better, significantly better, through 600 hours!  I’m just saying, I have found these Morrow Audio cables to be nothing short of miraculous. 

I can second the Audience recommendation in terms of tonal balance. However I’m not sure it will be a good match for Wilsons. Audience cables are fairly light gauge and Wilson speakers tend to be difficult (low impedance) loads and current hungry. I feel like I always see them with massive amps and garden hose cables. Something like Au24 SX may not let the speaker “breath” enough, but I’m sure Wilson owners and others can state with more certainty.

I like Cardas Clear and I think it’s one of their better cables, but as others have said it is not going to be as warm and sweet as the traditional Cardas sound. To me that’s a good thing because I find most Cardas to be a little rolled off and dull. Eg golden reference may sweeten things but I don’t think I’d be willing to sacrifice the life of the sound to get the tonal balance right.

One that I think might be worth trying is Crystal Cable. I’ve heard them in two very different systems and I was impressed with how detailed, open and natural both were, with not a hint of glare or brightness. One was with Audiovector SR6 speakers and a Devialet amp and it was super smooth and present. I don’t recall the model of cable but I believe it had a gold silver alloy. It did not strike me as bright as silver is wont to be - perhaps the gold is the trick. 
BTW, not surprised the Valhallas are burning your ears off. :) They can do great things in just the right system but seem super critical of any upper frequency energy.