Paula, if you compare the specs of the M2 and M3, you will see that the main difference is in the woofer size and the crossover. The graphs show that the M2 has a flatter response where the M3 has a bit of a boost lower down, and also goes a little deeper than the M2(about 10hz). I've not heard either of these speakers but if it's anything like the rest of the Axiom lineup, their goal is for uncoloured and detailed music reproduction. I'm sure you'd be happy with either(I'd probably lean towards the M3 esp if your not using a sub).

Half of communication is listening. You can't listen with your mouth.