Two weeks ago, executives at Sony placed calls to a handful of investors vying for its 36-story Manhattan headquarters that spans an entire block on Madison Avenue from East 55th to East 56th streets. The short list, which included competing groups led by Joseph Chetrit, Harry Macklowe and Joseph Sitt, had just vaulted over a deep field of big-league bidders, including Vornado Realty Trust and SL Green Realty Corp. Those who had cleared the first hurdle had agreed to pay $1 billion or more—and commit to a $100 million cash down payment for the distinctively topped, granite-clad tower designed by Philip Johnson in 1984 as the headquarters for AT&T. But Sony wanted more: an irrefutable demonstration of who truly had the financial wherewithal to pull off one of the city's highest-stakes deals in years.