Thanks for your response.
There seem to be two issues here:
1) Amplifier : Do you mean to say that the bandwidth of musical instrument amps is purposely designed to be non-linear at the higher frequencies? By non-linear, I suppose you mean that it filters out those ultrasonic harmonics - ie. like a low pass filter would though in this case "low" would be a fairly high threshold. I'm still confused however as what you're suggesting is that a recording of a piano does not have the same data as a sample of a note from a digital piano, which is taken from a real piano as well.
2) Speaker
If the typical bookshelf speaker such as the Axiom M3Ti is not meant for musical instrument reproduction, then what kind of speaker is? How would it be different from a normal speaker? I asked a similar question two months ago before I bought the M3's but I think the message board doesn't archive back that far.
Given that the piano will be used about half of the time that I use the speakers, it probably makes sense for me to change to gear meant for musical instrument reproduction rather than always be worrying about blowing out my speakers, not to mention the ringing I currently hear. Should I change the amp, speakers, or both?
Also, if amps/speakers made for musical instrument reproduction are different, I wonder how they would now sound with recorded music.
I appreciate any of your insights.