Re: driving the M80s on the Yamaha, be sure to see this thread
, especially Alan's responses.
I faced a decision somewhat similar to yours. I have a Yamaha RV-1105, rated at 5x85 WPC, which has a 4 to 8 ohm switch on the back for changing loads. In my case, Brent at Axiom recommended I stick with the M60s due to the power clipping potential that Alan describes in that thread linked above. Brent in fact said I should NOT get the M80s due to the potential for power issues with my particular Yamaha. I have no idea how the 1300 will do -- supposedly the 1400 and definitely the 2400 can handle the M80s well. Others on this forum have touted the 2400, so I have to believe it can handle the M80s handily. Maybe you can make some inferences about the 1300 based on its distinctions from the 1400/2400 series? You can learn more about the 2400's impedance switching in this Audioholics review by Gene DellaSalla
-- and I seem to recall that somewhere online he describes driving M80s very successfully on his Yammie 2400 -- I can't find the link to that, perhaps it was actually a comment here on the Axiom forums, but I know I've read this.
In sum, I'd definitely email Axiom for advice before proceeding. For what it's worth my wife and I are very happy with the M60s we bought in lieu of M80s, operating in a 14'X18'X8' room, 70/30 Music/HT .... I agree with others however that if you can handle the M80s, power- and budget-wise, you may as well buy them, just for the peace of mind post-purchase factor.