I am running M80's and M5 and can say you would be fine with the 5's replacing the 60's. I have moved the M5's to both surround and main L/R speakers and would be fine with the 5's as the mains. I have driven them with many different amps.
I also started with the VP150 and upgraded to the VP160. Having heard all models in all lines at the factory in comparison to each other, I don't feel I am missing anything with the 160. It was night and day difference for the better, so the VP180 could be better or overkill. There is a 30day trial period, so you could order both and send back which ever model loses you comparison!
