Yeah, (as I always say) don't listen to the dealer; listen to the speakers!
The salesperson's mention of the M22 break-in, as well as the effects of a "more powerful" amp, is essentially a BS. Ian, the Axiom founder and chief engineer, has openly stated that his speakers don't require more than 1-2 hours of "break-in," if any. No solidstate amp will make M22's bass "tighter" or "punchier" than what you heard (unless the amp you heard was grossly underpowered, which is very unlikely). As Craig said, this is a non-issue for you anyway, since you will be using it with a subwoofer.
With regard to the "suitability" of the Axioms for the rock and heavy metal genres, what the dealer said is again a BS. But it is true that the Axiom speakers are honest about "hot" recordings often found in the rock/pop CDs. Those recordings, intentionally EQ'ed to sound nice on FM radios, boomboxes and car audios, may present themselves as overly aggressive on the Axioms, simply because of Axiom's highly neutral and accurate nature. At any rate, it is VERY important for you to listen to the speakers with the music you like and are familiar with. You are the only judge here!
Good luck!!!
