recommendation for speaker wire to soften the highs if possible


Hello,
I need help. My problem is my system sounds harsh on the highs to me. Not extremely bad, but enough that I need to fix it. My system consists of Ryan 610's, oppo Sonica Dac, and a Belles 150a hotrod amp. Speaker wires being used are old monster cable from the 90's. I also have monster cable rca. I mostly stream through Tidal. My question is can I make the desired effect by switching cables or should I add  a tube amp or pre amp. My budget on the wire would be around 300.00
Thanks in advance for any suggestions
128x128gunmetalzin
How can you be sure that Monster speaker cables cause it ? It can be anything or everything. In any case, don’t buy unless you can return, or willing to sell what doesn’t work for you.
You don’t really want to soften the highs, you want a balanced and relatively distortion free sound. Maybe that’s in fact your objection - high frequencies distortion.
I have tested speaker wire and discovered that a lot of the harshness was actually due to stranded low quality speaker wire.  I found that solid-core remove so much of the harshness it was surprising.  I would look for some used Audioquest speaker wire and make sure you get only the gold-plated terminations (i.e. spade or banana).  The silver-plated connectors can make the highs too bright/harsh.  The same logic applies on the interconnect cables as well.
Thanks for the useful and quick response.
Inna I don't know if the cables are causing it and  high frequencies distortions the better term. I also know cables are a hot topic and I'm not looking to go down that rabbit hole.I just wanted some advice or experience from the members on certain cables that might help and be a cheaper route if I go for new cables. 
It sounds like you're using your Oppo as a preamp which could contribute to the sound you hear. Also, depending on the length of your speaker wires - assuming ~8' and not longer, you may have better luck looking for "warmer" interconnects to tweak your sound. Just as an aside, I think putting a tube preamp between the Oppo and your Belles will transform your system for better.
gunmetalzin,

I had the early nineties Monster "Powerline 2" speaker cable for some time.  If that's what you have it's Nasty Stuff.  I suggest the Acoustic Zen Satori I use (of course).  It can be easily found used at your price point.  It clears out the glare and edge in a huge way.  There is a slight lower-mid / upper-bass bump that can be pleasing in the right (not overly warm) system.