Axiom probably recommend you to keep your front speakers at small to keep the demaning load off your Denon and transfer it over the EP500.
It takes a lot more energy to produce low frequencies than high ones. If you set your fronts to large and LFE to both main and sub, your Denon amp will have to work that much harder to reproduce low frequencies to your main's (M80’s). That seems silly when you have a 500 watt amp in your EP500. It’s all about adding headroom for your amp to prevent clipping.
When you go to a monster receiver or separates and have 150w/c or more to play with, then there is more headroom for your amp, and you can set the mains to Large and LFE to both.
Your M80’s are capable of handling tremendous levels of low frequencies, but you amp may not. It’s all about headroom and not clipping!
Paul
