Hi Melbguy, I can only make some conjectures, based on what I know about M925 and M825, which is not yet a great deal....
M825 outputs 440W instead of the 440W of the M925.... Furthermore, the external 2400W power supply of M825 serves two channels instead of one. I suspect that, as a consequence, M825 might deliver staging and images that are slightly smaller than M925, with perhaps some proportionally reduced authority.... However, the two devices are supposed to be otherwise internally quite similar except for the obvious differences caused by the stereo vs mono topologies... So I suspect that their sonic characteristics may be very close to each other.
As Corus supplies an output impedance of 60 Ohms, it will be compatible with either amps, and should not be a factor on the choice of speakers.
Unfortunately, I am not familiar with the Avalon Compass speaker... So it is difficult for me to make any meaningful guesses on a specific match of M825 to Compass.
Guido