The LFRs, without DSP, don't sound like their passive siblings.
The LFR660 would be better than an M80 for your space. The M80 will boom like the Dickens. Every Axiom passive I've had in my similar-sized living room has boomed - some worse than others. Even M2 bookshelves and OW although those needed only a touch of bass attenuation.
The active LFR1100 have been the only speakers ever that have not needed any type of correction in my 2000 cu ft living room or 4200 cu ft main space. The bass is something to behold!
One look at the frequency response curves of the M80 vs the LFR660 tell me the 660 will be better. Just look at how much better behaved the 660 curve is particularly in the bass. Sorry...Andrew and Ian really tried with the M80 but it's a bit of a beast to tame.
One other thing. I expect the 660 will give you improved imaging and soundstage. It will acoustically disappear better too. And it will offer higher fidelity across all bands. I guess that's 3 or 4 things.
