Hi PT,
I checked the specifications and since the amp has output transformer taps for 4-ohm loads, you should be just fine using it for the M80s.
Keep in mind that, unlike solid-state amplifiers which essentially have an output impedance of 0 ohms, the output impedance of a tube amplifier is never zero, and its higher output impedance may interact with the impedance curve of the loudspeakers. That may affect the linearity of the frequency response (i.e. it won't be as smooth as a solid-state amp) in which case you may find that the amp does indeed sound different from your usual solid-state amp.
As to other mystical qualities attributed to tube amplifiers (added "air" and the like), I believe those exist largely in the active imagination of the listener.
It should be fun to experiment.
Regards,
Alan
