Its called a typo
You sure can use a single M3 as your centre channel. Placement can be more difficult since you will want to set it vertical (just like the mains). If you have a small to medium sized room and you can achieve proper placement, this would be a great choice.
You can also use a horizontal centre channel such as VP100 and VP150. Generally the VP100 is used in small to medium sized rooms where your listening position is less than 13ft away. In a large room the VP150 will be the best choice. Saything that you can still use the VP150 in a smaller room. It just depends how much you want to spend. Axioms line up of speakers all have the same general design philosphy so they can be mixed and matched as you please.
Cheers!
