There are lots of people using pro amps from Crown,Yamaha, Behringer, Peavey etc etc very successfully with all sorts of speakers. In fact its quite a popular route to go. It is true that fan noise might be an issue, however depending on the popularity of the unit in question you choose they are a lot of DIY guides about replacing the fans on many of them.
If you have the M80's and thinking about the VP180, if there are any speakers that can take advantage of more power it would be them. A well designed pro amp will be able handle low impedance speakers like the 80's and VP180 at high output levels with plenty of headroom to spare unlike a receiver.
I agree with Dakkon and it is a very cost efficient way to get lots of power not just a measly 100 watts more.
