No I dont believe that you can quite replicate the full range of motion under tension with a dumbbell. You know that it is very hard to keep that tension on the muscle even using very strict form. You usually just miss or have a "blank" space at the very top or the bottom of the curl & normally you will fail on the positive before the negative, so unless you use a spotter you cannot achieve this easily.
Though I understand your enthusiam for variety and range of motion, I must advocate the usage of free weights over cables.
However, it is important to also understand that cables have their place in bodybuilding - with some, not all bodybuilders.