It's weird to compare a bookshelf speaker (m22) to a tower speaker (EMP 5is). The EMP's will likely be able to play louder and deeper. You should compare the EMP bookshelf to the Axiom m22. I think you will find the M22 to be a more impressive speaker.
However, the EMP towers have been getting a lot of high marks at AVS. They look gorgeous and they have RBH Sound people involved, one of the oldest and most respected American speaker brands.
See:
http://www.avsforum.com/avs-vb/showthread.php?t=1388934Also since you already have an Axiom center, it makes sense to keep your front speakers Axiom (as others here mentioned) unless you plan on changing all of your speakers.