Other than the obvious cosmetic problems, dings, scrapes etc. I would listen for odd noises such as buzzing from tweeters or one speaker sounding different/off from the opposite pair with full 5 channel stereo being used as the source from the reciever, this way they should all be playing similar sounds, using a mono setting would work even better. Other than that just listen to YOUR music and movie types to see if the Axioms fit your music/sound quality tastes, just like any other speaker from a store.
