Amber has a much stronger flavor than biscuit. Biscuit really won't impart the flavor that amber malt provides. In my experience, amber malt produces a roasty flavor. Ounce for ounce or pound for pound, it's not going to be quite as intense as black patent, but a little goes a long way. Order some Thomas Fawcett amber malt (instead of crisp!!!) and you'll be ok.