actually, I like bent over rows with dumbells sometimes. When doing them with dumbells instead of a barbell you are forced to recruit a bunch of different stabalizers. Also, you may find that one side is weaker than the other, so this will allow you to overload each side in a different manner. To make them more challenging try doing them recipricoal or unilateral (one after another, alternaing reps between each hand), or just do them like a barbell row. Also, usually people do the one arm dumbell row (which is a great exercise) with a neutral grip and mainly work in the sagital plane, the bent over barbell row however can be done with a pronated grip so that it can be in the transverse plane easier, or a reverse grip (more in the sagital plane).