My M80's are bi-amped. And I like it that way.
I had the extra channels on my amp and was using Canare 4S11 quad-cable anyway, so one afternoon (many months ago) I decided to bi-amp one channel to see if I could possibly tell a difference. Just split the RCA-outs from my AVR and fed them into 2 pairs of channels on my amp. Definitely didn't use any sort of external crossover.
Well, after a few CD's worth of L/R balance listening, I was actually preferring the bi-amped channel. I swapped the channels to make sure it wasn't the speaker, and still preferred the bi-amped channel. Believing full-well that it was just my imagination, I asked my wife for help and told her that I had re-wired one speaker, and asked which one she liked better. She too, picked out the bi-amped one. We both though the bi-amped channel was a bit 'fuller' on the bottom end. The bass was just a bit better and the sound was just, well, a tiny bit more pleasant. It was subtle, definitely, and not really apparent on every recording. We just preferred it.
So from that, I bi-amped both and my system has stayed that way ever since.
