interested to hear from fred k since he visits that forum and also has the system I am considering.
I am not sure what more information I can give you. Jamie at audioholics dosn't like the M80s, I do.
I guess the only thing I can add is that differences in sound are much more subtle than most people would have you think. Alan Loft, in his comparison of the M80 and another speakers, suggested that a 2db difference in the midrange, the frequency of sound we are most sensitive to, is audible but subtle.
As you move up in frequency, its is going to be less and less audible until it makes no difference. Heck, most people can't hear anything above 16KHz and if you are 40+ possibly no more than 12KHz.
Independant anechoic measurements of the M80s show that the speaker has a very flat frequency response. Period. Done. End of story. Can you hear the difference in the high end vs a speaker where it rolls off starting at, say, 8KHz? Probably a subtle difference.
Have you ever listened to live music in a good hall? That is the kind of sound the M80s will give you. Because of the flat frequency response it will be like having a seat in the first 15 rows of a show. If the high end response is rolled off slightly, it is like having a seat at the back of that same good hall. Is the sound in either seat bad? No. Would you notice the difference in seats if I didn't write this? No.
The M80s are a great speaker. The Salk Songtowers are probably also a great speaker(I havn't personally heard them). The Studio 100s are also a great speaker...
Stop worrying, start enjoying. Whatever you pick, unless its Bose, will be good.