The Dynaudio Acoustics M3A is a three way monitor, used as a stereo pair. These are main monitors, and I'd be severely surprised if you were to ever see these being used as anything other than a main monitor considering the sheer size and price. These monitors are active, so at least you don't need a super powerful amplifier to go along with this monitor. The built in amplifier is a 2-way crossover that consists of two separate amps per each speaker. These monitors can be used for any application.
The sound of the Dynaudio Acoustics M3A is really an experience. They things can get incredibly loud, and are really the perfect main monitors for any larger studio. They say that these are best in a medium sized room, but I would imagine that they would work fine in larger rooms as well. I'd stray away from using these in smaller rooms however, as they will blow you away! I haven't done any mixing on these, and I'm not sure that they would be ideal as they are almost too good sounding for mixing.
You should only be finding the Dynaudio Acoustics M3As in larger professional recording studios, as this is where these belong. They are really the definition of main monitors and are perfect for playing back all genres of music. They can get incredibly loud, which is I guess the point with three way monitors of this type. I can't say that I'd recommend these to anyone putting together anything less than a large studio, as they are too pricey and large for anything. If you are looking for an incredible set of main monitors, these will cost you, but this is definitely everything that you should be looking for in large main monitors, as I really don't feel that you could ask for anything more.