Stocks stepped out to early gains in firm trade Wednesday, despite a welter of mixed economic and company reports. The Dow Jones industrial average and the S&P 500 each posted 0.5% gains. The Nasdaq was hot on their heels, up 0.4%. Volume was briskly higher in the stock market today, up 21% on the Nasdaq and 6% higher for the NYSE compared with trade at the same time Tuesday.