Well, mismatched centers and L/R speakers generally have tonal problems. As the sound pans across the front three, when it hits the center it sounds different. How much different depends on which speakers, but going from an aluminum dome tweeter on the Energys to a Klipsch horn, I don't think it will be pretty.
But it might sound okay to you. If you can try out the speaker for free, you have nothing to lose.
Don't believe everything on the Interwebz! A duck's quack DOES echo!