Just going by your original post I think you would find the M80s more to your liking. You say you want a new amp to open up the M60s, as the others have said that won't do it, but the M80s are more open and certainly more forward than the M60s. Are you cranking it up to make it easier to hear the details/vocals?
Mojo and I have compared his M80s to the M60s I recently purchased. I found the M60s to be not as forward as my older M22s and had heard so much about the M60 that I bought them with out hearing them. The M80s sound more like the M22s, more open and easier to hear the details than the M60s. My M60s are going back next week for M80s which should be arriving shortly.
If you can, audition some M80s which is truly the only way for you to know if they will help. If you can not find M80s try Paradigm Monitor 11s they sound very similar only the 80s are just a little more detailed/open (fill in your own adjective here)
