I agree 101%. The point isn't so much to lower the frequency response. It's to improve the overall low frequency response in your listening space.
Although the placement of your main speakers may be ideal for the highs and mids, chances are that the low frequency can benefit from the addition of a pair (or even better four) subs. And don't simply plunk a sub next to each of the mains. Any low frequency response problems will be linked to that spot in the room, so the subs should be placed where they perform best, instead of where they look good.