recommendation for speaker wire to soften the highs if possible

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.

People mistake frequency response for time and phase errors. When rooms interact with time and phase errors it is entirely possible to have large perceived differences in the 2-5kHz range.

Western Electric made cable for balanced circuits with extremely limited bandwidth. It was often difficult to understand a well know acquaintance until one had ’learned’ their voice over the telephone.

Cables are no more a Band-Aid than an amplifier. It is possible to take the best of everything and make two systems, one of which will rip your face off and the other will put you to sleep. Put the systems in different rooms and both could be great.

For the googlth time, specific product recommendations in fora like these are not worth the bits to transmit them.

I am not saying that Duelund Wire lowers the presence range by any amount of dB.  I am saying it changes the tone and presentation so the upper mids and highs are more natural and real sounding. Less Hifi, electronic and forced sounding. No band aid here, just part of putting together a complete system that sounds right.  

I've said all along that it is likely an equipment issue. I had a similar issue with my DAC, and cleared it up with a reasonably priced hospital grade isolation transformer, that and Deulund cables, which are just good neutral cables, should be under $300 or so, and in many system would cost far less that trying new gear. YMMV

Perhaps you are expecting more than the 610’s are meant to deliver.  I often find myself increasing volume in an attempt to make my smaller speakers sound as immersive as my floor-standers.  Before long, the soft dome tweeters start sounding stressed.    The Ryans’ felt pad tweeter surround suggests to me that the tweeter section may already be working against its physical limitations.  There is a reason some designers are moving toward lighter, faster metal domes (listen to berrylium), and AMT planars.
Don’t laugh.  Try a sub.  It amazes me that just a little additional bottom end can tame perceived tweeter harshness.  
Caution: Make sure you visually hide/disguise the sw as much as you can before your spouse sees it. Use your imagination to make it more acceptable (a flower stand or sculpture base).  At least throw a tablecloth over it to let the sound work its magic unseen
Good Luck, and call the folks at Ryan.