Stocks opened lower in firm trade Monday, with much of the early action revolving around analyst reports . The Nasdaq, S&P 500 and Dow Jones industrial average were each down 0.5%. Volume climbed, up 9% on the Nasdaq and 26% higher on the NYSE compared with Friday morning's trade. Some key tech stocks were under some pressure in the early going, partially due to a handful of analyst downgrades. Apple (AAPL) slumped 2% after a note from Barclays