I heard the 180v4 and it sounded no different than my 160v4. I can dump 950 peak Watts into my 160 and it sounds composed. I haven't tried to dump more than that via the 1500. The 180 can certainly take more though and go louder.

I can't say enough about the v4 tweeter. I think you will notice a difference there.

I suspect, based on what I know of v3 vs. v4 M3, the cross-over has been improved.

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