The stock market was rallying broadly on Wednesday, but Goldman Sachs was giving the Dow a big boost. With the Dow up 657 points, or 1.6%, Goldman Sachs’s 5% gain added more than 175 points to the Dow on its own. The Dow weighs its members by stock price rather than market cap, so Goldman Sachs stock, with a stock price right around $600, is the index’s heaviest hitter.