I think that Rotel RB-1080 would be great with your M80s. It is rated 200wpc at 8 Ohms, that means around 350wpc at 4 Ohms (correct me if I am wrong). Great power amp. MSRP in USA is 1K but you can look for one used on ebay and audigon, since the Rotel power amps (and power amps in general) do not depreciate vey quickly.
And yes, if you already have a receiver and don't want to go through selling it on your own, it is a wise idea to purchase a 2 channel power amp to power the fronts. Otherwise, if you start something from scratch, and plan to have an outboard power amp, just go for the preamp/amp combo and forget the receiver.
