As its projected launch date of Jan. 6, 1997 draws near, NBC's newest night-time soap, "Sunset Beach," has signed several hot young actors in featured roles. Ashley Hamilton, who has appeared in the films "Beethoven's 2nd" and "I'll Do Anything," is set to play Billy Felder, a freshman at UCLA. Sarah Buxton previously appeared on television in shows including "Walker, Texas Ranger," "Renegade" and "Silk Stalkings." She'll be playing Annie Douglas, the sexy and spoiled resident of a local beach house.