Also, Builders FirstSource ( BLDR ) said it was buying rival construction supplier ProBuilding for $1.6 billion, sending shares of BLDR to a seven-year high. (+) BLDR (+59.86%) Agrees to buy ProBuild Holdings or $1.63 bln in cash. Stocks were cautiously higher Monday ahead of a slew of Q1 financial results from major banks later this week and a heavyeconomic calendarincluding data on inflation, manufacturing and the housing market.