First, there is the adage of "the right plant in the right place." When you say, "I have heard that they get gigantic." that is something you should have found out beforehand. Kind of like getting a puppy. However, there is a difference in don't need to be pruned and can't be pruned. How big will be too big for you? They will get around six feet, but the same plant in different sites will grow to different sizes, depending on how happy it is there. Do you want the border for aesthetics or could you use the screening? If you want to keep them lower/smaller, pruning each year after flowering is an option.
One suggestion for replacement is Indian Hawthorn. It is evergreen, has small pink blooms in the summer and is tough as a holly. Gets 3-4 feet high and a little wider than high.