WASHINGTON - Amazon.com Inc's planned second headquarters in northern Virginia cleared a key test on Saturday when local officials approved a proposed financial package worth an estimated $51 million amid a small but vocal opposition. Amazon in November picked National Landing, a site jointly owned by Arlington County and the city of Alexandria, just outside Washington, along with New York City for its so-called HQ2 or second headquarters. That followed a year-long search in which hundreds of municipalities, ranging from Newark, New Jersey, to Indianapolis, competed for the coveted tax-dollars and high-wage jobs the project promises.