One more thing to consider (and something you asked about) is the source player -- and how it's hooked up. Some may disagree, but I find my Toshiba DVD is not a great audio CD player when it's hooked up through the digital coaxial to my Yamaha receiver. There are technical explanations, but the bottom line is in A/B tests with my ancient Sony CD changer, the CD changer always gives a richer sound, without some of the brittle highs heard via the DVD.
I imagine the DVD player combined with placement problems with the M80s could be producing the bright highs you're hearing. When I got my M60s, I was blown away, but I also heard cymbals and clear highs that I had never heard before on my CDs. The new sounds were great, but they interacted with my room in ways that could sound harsh. The new awareness revealed some of the reflections in my listening room. This led me to add thick yet translucent curtains over two sliding glass doors, and even my sarcastic wife admits this made an improvement in the sound quality of the room. She loves the speakers, possibly more than she loves me (certainly true from time to time). Bottom line: The room adjustments tempered the highs (which were from the room, not the speakers ... or rather, resulted from the excellence of the speakers IN that room). Now, I still get a harsh kind of high on one CD out of the 300 in my collection -- Sam Phillips' Martinis and Bikinis. But I've never tried this CD on another system, so the mild harshness quite likely comes from the recording.
So tinker a bit before you give up on the M80s.
If you make these adjustments (including the placement deal -- make sure they are 8-10 ft apart and at least 18 inches from the wall, preferably 2 feet) and still aren't sure, try to borrow some towers from a friend, to help figure out the source of the sound issues -- whether it's the speakers or something else. People have sometimes voiced concern with highs on the M80s, and you can do a search on "capacitor" in this forum to learn what some have done to deal with it. So you're not the first person to be concerned.
Birdman
