I just looked at the forum and saw your message. Sorry, but I don't check the site often.

My experience with the M200s is that there is a low level of high frequency hiss if I am very close to the speaker when the pre-pro is turned off. It is not possible to hear it from more than 2 feet in a quiet room. Anything more than that may be a problem with RF or EMI from outside sources. I have been extremely happy with my M200s. I don't believe that I could improve my amps with my system. Please let us know what you find out. Perhaps you could try to isolate the amps and the speaker wires and see if the hiss goes away.