My system's high frequencies hurt my ears

Get some GIK acoustic panels and treat the 1&2nd reflection points as well as the wall behind you. They can also be used on the wall behind the speakers.

Please tell me about your room. I can near guarantee you that these 242 and 244 GIK panels will cure the problem and greatly improve your music.
All glare and harshness will be gone. Turn up the volume and the music will swell and grow in size and impact, but not in harshness.

Had the Mirage M1si from 1996/2009, tried all kinds of positioning. With bipolars the rear firing speakers will fight the room much worse than conventional designs. I only found partial contentment in my current large room with them around 3ft+ from rear wall. What works in your room may be different as bipolars can be a PITA. Looking back had I been aware of sites as this I'd of moved on years sooner.

Try toeing the speakers in until the axis of the speaker crosses well in front of your head. Some of the excess highs might be from the first reflections from the side walls. This will also change the back wave quite a bit and could lower high frequency energy off the back wall as the sound waves have to travel further to reach you.

FWIW, it is not a straight forward speaker issue no matter how logical that may seem due to metal tweeters reputation. I have had similar problems with silk domes etc. Spend a lot of time positioning and repositioning your speakers before you decide to replace them. That is, at least the cheapest alternative. You might also consider trying, as suggested, deadening somewhat the rear wall.

FWIW, going back to your speaker wiring and I/C's. Nordost gets a lot of sales based on how it presents the high frequencies. Great clarity, at least so it seems. For a while. But what I think occurs is that the highs are not in balance with the mids and lows making the sound appear bright. I worshipped mine for about 3 months. Try a cheap experiment - get some Canare 4S11 Star Quad speaker cable and some Blue Jeans I/C's and use them as a benchmark for other brands - they are really inexpensive and good. They have a large following for just that reason. If after repositioning your speakers and treating the walls behind your speakers and using this wire you still have high frequency problems then perhaps it is time to move on. Unfortunately, as you may find out as many others have, this may not be a solution to your problem and that is why I emphasize further exploration with what you have.

I have tried Blue Haven and it is nice but it is quite bright and slightly etched so consider another cable. Agree with pointing speakers away from towards you. Try straight forward. Beyond that, soft dome tweeter speakers -- perhaps Dynaudio or Dali.