I'm no expert but in uneducated terms, one of Axiom's claims to fame is how they dynamically apply unused power across whatever channel needs it at the time. If your fronts need more power and your rears are nut using it at the time, the free power gets channeled to the fronts where it is needed.
With this in mind, most amps/receiver's wattage ratings are stated "per channel" but are actually based on the box only driving one or two channels at that time. If nothing else, Axiom freely posts wattage provided for all combinations of channels driven. You can check out these numbers on thier Amp product pages. Much better peace of mind.
In your case, you are dealing in stereo only so all of the above is not as much of a concern. As John would point out, Unused power is just that, unused. I'd feel quiet comfortable with your choice for your needs unless you like it overly loud (beyond safe levels).
