Barkeep, of course it may be that the 602s weren't quite as "gently used" as you thought. Although it would be unusual for the woofer rather than the tweeter voice coils to be damaged, if they were subjected to some extreme low bass load it's possible. The 602s should have good mid-range and bass down to at least 50Hz. The amplifier power has nothing to do with this.
Since they have two sets of terminals, connect your speaker wire to the lower ones and remove the connecting strips so that only the mid-woofers are powered. Play test tones in the lower ranges to see if one or both mid-woofers are either very low in level or completely silent.
