If you're getting a powered sub, then it does not matter whatsoever whether your bookshelves go down to 42Hz or 49Hz. More important is how the speakers perform to your liking, in any case.
As for the high frequencies, it's really irrelevant whether a speaker goes up to 22kHz or 30kHz since human hearing maxes out at 20kHz, and for most individuals, much lower. So unless you're playing SACDs of dog whistles for your pet's enjoyment, this is also a non-issue.
Get the MAs if you like them better than the 685s, but not because how high and low you think they can reach, especially in this case.
As for the high frequencies, it's really irrelevant whether a speaker goes up to 22kHz or 30kHz since human hearing maxes out at 20kHz, and for most individuals, much lower. So unless you're playing SACDs of dog whistles for your pet's enjoyment, this is also a non-issue.
Get the MAs if you like them better than the 685s, but not because how high and low you think they can reach, especially in this case.