BrotherBob,

I doubt the M80's would give you that much better sound. If you are going to buy another pair anyway for a second system, then get them as long as you can afford them. you can't go wrong with M80's unless you are putting them in a very small room (i.e. 12 by 10).

What size room are you thinking about putting the M80's in? Do you listen very loud? Are you going to add a sub to them?