Durga is not nearly so fierce as people assume Her to be. She takes form whenever She is needed, whether that is because you are struggling spiritually with loss of hope and belief or battle evil tendencies. Kali, too, is not so fierce; at least to me. She has drawn me to her as Durga and Kali; murtis of Parvati are very very difficult to get your hands on as She is often depicted with Shiva. I have murtis of Her as Durga and Kali and a small, much neglected murti of Her as Lakshmi. It is difficult to find small, appealing Saraswati murtis as well... Let us not forget that Shri Ramakrishna was enamored of Kali Ma.
There is a quote about Kali by Ramakrishna in the terrace of the temple I mentioned You may have seen it, it's the one saying how the infinite is dark and black.