recommendation for speaker wire to soften the highs if possible

I certainly agree about Cardas, I tried that for my DAC before switching over to the isolation transformer. It was an improvement, but it was a bandaid not a fix.

You might try a overpriced  power conditioner that helped for me 

I love reading the responses to these sorts of questions. Every answer a different notion. Try this try that, no it's your frammims.. Sorry you need a new _______. (twenty different things)If you do them all, you would have spent the equivalent of a down payment on a new home. And still have no answer. The pitfalls of audio madness.

Some are actually true and helpful. Hard to weed through it all. 

Personally, I don’t believe a cable can effect the frequency response of a system, nor act like tone controls.

When someone describes a cable as “taming the high end” to me it seems like he’s describing a room interaction problem with the speakers, a speaker shouldn’t naturally sound shrill unless it’s badly designed or is having some serious first point reflection issues.

So basically, if you’re to believe these people, they are claiming that their cables are lowering the 2-5khz range by a few dB.

I’m not a electrical or sound engineer or a scientist of any kind, but that just doesn’t seem logical or scientific to me.