Here in zone 5b I have had good results for years just by putting my potted Amaryllis in my cool, dry, and fairly dark basement once the leaves have withered in late fall/early winter. I don't water them at all over the winter, and in early spring I will see new growth popping up out of the corm/bulb/whatever it is. Sometimes I will bring them up into a sunny spot and water, but I can and have actually left them in the basement until it was warm enough to put outside for the summer. They've been in the same planter for years. There is a dahlia in that planter too, so it overwinters in the same way.