I have both in my possession but need to get rid of one. Whichever I go with will be in my Std Cab Ranger and will never power a sub needing more than 1000W. The M.80 is about 800W @ 1 ohm (supposedly can put down a bit more than that) while the NINe.1 easily does 1400W @ 1ohm (truck hasn't dipped below 13.8V).
I just can't make up my mind. The ONLY reason I can see to keep the M.80 over the NINe.1 is that the M.80 is significantly smaller. Right now I'm powering an eD 13Av.2 in a 2.3 cu ft ported enclosure and the vehicle is much more SQ oriented than SPL.
Please don't hesitate to lend your thoughts. Whatever I choose to not use will be sold!