I read somewhere that there may be issues with the Emotivas and the M80s. I'm not sure if that's because the 300 Watts isn't enough hence:
2. Emotiva XPA - 2 (Two Channel rated at 500 watts into 4 ohms) and I'd just run the M80s with this.
Both of these options are much cheaper than anything else I've seen, but I'm slightly afraid of 2nd hand comments I've seen regarding people having problems
I have the Emotiva XPA-3. First of all let me say that for the money I got far more with this amp than I ever dreamed I'd get. However, seeing as you have the M80's I cannot recommend this amp as there have been many issue's between the 'X' series amps and the 80's. I myself had a bit of difficulty making them play nicely, not nearly as bad as some had it, but enough that I can see why most M80 owners shy away from Emotiva.
Which is a shame because like I said, they really very nice amps at an outstanding price point. If you had the M60's I would not hesitate to recommend them.