The M5 is indeed much, much better than the M80v2. If you think the M80v2 is clear with the 1500, wait 'till you hear the M100.

You can always trade in the 180 for a real 180 and ask for another signature. It would be worth doing if you have pre-v4 tweeters. Also the aluminum dust cap really helps with heat dissipation and improves linearity. A lot was done between v3 and v4 that doesn't get talked about.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated