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

op-if you haven't dropped dead from reading all this yet, good work.
I too need a less forward top end for my ears. I met Ray Kimber at 
RMAF last Sept. He made me a pair of the 8's custom split.
5 strands go to the woofer and 3 to the mid/upper.
all copper. About $300 as I recall. Love them. I was shopping
the Cardas market before Kimber as they have a rep for being
softer up top. But those will cost you 2-3X what the Kimbers do.
No silver or Nodoze for you.

I have tried them all and found out 
that Black Cat #3232 the best.

I’ve also fought against overall brightness with metal domes and DAC direct into SS amp, and had Eclipse 7 speaker cables before upgrading to Cardas Clear. Either could work for you. The eclipse had more dynamics and midbass, but the Clear is just better overall and not bright nor dull. The treble is really extended and clean and it has great low bass. The eclipse had a slight hardness or glare in the low-mid treble which became obvious in comparison.

Honestly, I would suggest trading out that Vahalla PC for a Cardas Clear which I also have on my ML 532H amp. You may lose a little in clarity, but man, what you will gain in terms of system balance. This trade will actually earn you money. At a recent audio show, I noted that Cardas Clear was a very popular choice.
I've never liked Transparent, but have only a couple short experiences in showrooms. Good Luck!

Wire World Eclipse

Going from some generic twisted copper cables without terminators to a $2000+ per meter speaker cable is quite a jump. You should experiment more in the low end before you take the plunge. Who knows you might find something you like along the way.

Like others have mentioned I would avoid all plated cables for now and stick with pure copper. All of the plated speaker cables I tried either sound too bright or harsh with my system (YMMV). I would also try some solid core cables instead of the usual stranded construction. Get a pair of the Audioquest Type 4 "no frills" cables audioadvisor sells and see what what you think. For me they improved the bass and low end punch vs a simple twisted stranded pair. They also had a pleasant midrange and I didn’t notice significant brightening in the treble.

Considering the amount you are willing to spend trying it should be a no brainer. You can get an 8 ft pair with bananas for $110 shipped. Then if you like it work up the Audioquest solid line. They should have the same voice.
https://www.audioadvisor.com/prodinfo.asp?number=AQT4NF&opt=474|492|494|498