DPA,
I may be the person that has heard both but not together, but here are my thoughts eitherway
I did like the infinities - they seemed to be a very good value for the money. Up to the point when I heard them, I had only heard other mass market speakers (polk, viena acoustics, klipsch, Energy, Paradigm, etc.)
After hearing the M60 and M80's though, I found no comparison. While clear, the infinities lacked the high end and mid range detail. They are a much more "laid back" speaker, and the M60/80 is a more "forward" or "bright" speaker.
My longish
journey left me realizing that I liked the "brighter" sound quite a bit more than the "laid back" sound of many other speakers.
Obviously, your mileage may vary
Have fun!
