Phil, you should probably take a look at the reviews of the M3s and M22s which can be found easily at ecoustics.com. The SoundStage reviews which include NRC measurements are especially worthwhile. In general it can be said that the the M22s have a bit flatter lower midrange and a little more clarity. The M3s have a small bump in the upper bass which creates an impression of greater "fullness", especially if used without a sub. I have the M22s and they're about as good as it gets in that type of speaker, regardless of price.
