subwoofer for Harbeth P3ESR

Question is basically would anyone consider using a sub with these compacts?
Does it take away the mid range they are noted for or add more bottom end without compromising sound ?
Personally I wouldn't use a sub with the P3ESR and listen to it as is for the sake of simplicity. If I want more bass or scale I'll just consider a larger model in the Harbeth line if the room can accommodate. Having said that I've tried a sub with the P3ESR and it blended in quite well. Bass augmentation usually works better with fuller range speakers though.